Hướng dẫn javascript cheat sheet github - javascript cheat sheet github
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Dựa trên học X trong phút y. JavaScript (JS) là một ngôn ngữ được giải thích năng động cung cấp năng lượng cho web. Nó được sử dụng rộng rãi trong các trình duyệt (trong đó các tập lệnh JS được giải thích bởi các công cụ JavaScript như V8 của Chrome) và ngày càng trên các máy chủ (trên môi trường thời gian chạy Node.js). JS là ngôn ngữ kịch bản dựa trên nguyên mẫu với các hàm hạng nhất và gõ động. Do tính linh hoạt của nó, JS hỗ trợ nhiều kiểu lập trình bao gồm bắt buộc, hướng đối tượng và chức năng. Đây là những gì tất cả những từ lớn ở trên có nghĩa là: TODO: Thêm 8. Thư viện hữu ích (Lodash, JQuery), 9. JavaScript trong trình duyệt, 10. NodeJS Mọi thứ trong JS đều là một đối tượng hoặc nguyên thủy. in JS is either an object or a primitive. tôi. Nguyên thủy: số, chuỗi, boolean (và một số đặc biệt)// JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is ii. Các nhà khai thác AKA Các chức năng được viết một cách kỳ lạ// Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false 2. Cú pháp cơ bản hơntôi. Biến// Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined ii. Mảng// Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false iii. Cấu trúc logic và kiểm soát// The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; } 3. Đối tượng và chức năngtôi. Các đối tượngMột đối tượng chỉ đơn giản là một bộ sưu tập không có thứ tự của các cặp giá trị khóa. // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff); ii. Chức năngChức năng là các loại đối tượng đặc biệt! Các chức năng có thể có các phương pháp và thuộc tính của riêng chúng giống như các đối tượng khác, nhưng chúng hiếm khi được sử dụng theo cách đó. Hãy nhớ rằng, các chức năng trong JS là hạng nhất. Có nghĩa là chúng có thể được gán và truyền giống như bất kỳ biến nào khác có thể. Các chức năng đặc biệt ở chỗ chúng có thuộc tính tên tùy chọn và thuộc tính mã (là phần thân của chức năng thực sự làm công cụ). Mã của chức năng được thực thi bởi toán tử gọi // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false0. // JavaScript functions are declared with the `function` keyword. // This is a function statement function myFunction(thing){ return thing.toUpperCase(); } // This is a function expression var makeUpperCase = function() { return think.toUpperCase(); } // Note that the value to be returned must start on the same line as the // `return` keyword, otherwise you'll always return `undefined` due to // automatic semicolon insertion. Watch out for this when using Allman style. function myFunction() { return // <- semicolon automatically inserted here { thisIsAn: 'object literal' } } myFunction(); // = undefined // JavaScript functions are first class objects, so they can be reassigned to // different variable names and passed to other functions as arguments - for // example, when supplying an event handler: function myFunction(){ // this code will be called in 5 seconds' time } setTimeout(myFunction, 5000); // Note: setTimeout isn't part of the JS language, but is provided by browsers // and Node.js. Các đối tượng chức năng thậm chí không phải được khai báo với một tên - bạn có thể viết một định nghĩa hàm ẩn danh trực tiếp vào các đối số của người khác.anonymous function definition directly into the arguments of another. setTimeout(function(){ console.log("It's been 5 seconds!"); // this code will be called in 5 seconds time }, 5000); Điều này đã dẫn đến một mô hình chung của "các chức năng ẩn danh ngay lập tức", ngăn chặn các biến tạm thời rò rỉ vào phạm vi toàn cầu. Biểu thức chức năng được bọc trong ngoặc đơn và sau đó được gọi bằng // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false0"immediately-executing anonymous functions", which prevent temporary variables from leaking into the global scope. The function expression is wrapped in parenthesis and then is invoked using // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false0 (function(){ var temporary = 5; })(); temporary; // raises ReferenceError permanent; // = 10 Một sự khác biệt quan trọng: nguyên thủy vượt qua giá trị trong khi các đối tượng vượt qua tham chiếuPass by Value while objects Pass by Reference // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is0 Từ khóa // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2 trong các phương thức, luôn luôn đề cập đến đối tượng mà phương thức được gắn với. Tuy nhiên, nếu phương thức có hàm bên trong, // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2 của nó đề cập đến đối tượng toàn cầu. Một số coi đây là một lỗi trong JS, vì vậy thực tiễn tốt là tạo và sử dụng một biến gọi là // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false4. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is1 iii. Bind, Gọi và áp dụngCác chức năng không gắn với các đối tượng có thể sử dụng // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2 và vẫn hữu ích. Xem xét ví dụ này. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is2 Để sử dụng nói, chúng ta cần sử dụng các phương thức .bind, .call hoặc .papply, có sẵn cho tất cả các chức năng. Tham số đầu tiên của các hàm này là đối tượng trở thành // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2 trong hàm.all functions. The first parameter of these functions is the object which becomes // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2 within the function. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is3 Các phương thức gọi và áp dụng cho phép chúng tôi thực hiện một cái gì đó gọi là mượn chức năng.Function Borrowing. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is4 Phương pháp liên kết cho phép chúng ta thực hiện cà ri chức năng.Function Currying. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is5 4. Thực thi chức năng, phạm vi biến, đóng & gọi lạiMột vài khái niệm quan trọng:
tôi. KéoTrước khi thực sự thực hiện bất kỳ mã nào, công cụ JS trước tiên xem xét tất cả các khai báo biến và câu lệnh chức năng và đặt một số không gian bộ nhớ để chúng di chuyển chúng một cách hiệu quả đến đầu mã. Điều này được gọi là nâng cao.hoisting. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is6 JS luôn đồng bộ (thực thi dòng mã 1 tại một thời điểm và theo đơn đặt hàng) và chỉ số đơn (chỉ 1 lệnh tại một thời điểm). Tuy nhiên, JQuery, Trình xử lý sự kiện và các cuộc gọi AJAX sử dụng các cuộc gọi lại dường như không đồng bộ. Các cuộc gọi AJAX được giao cho một phần khác của trình duyệt (bên ngoài động cơ JS), đó là lý do tại sao chúng được chạy không đồng bộ. Khi cuộc gọi trả về hoặc nếu có người dùng nhấp, thì các sự kiện này sẽ điền vào hàng đợi sự kiện. Động cơ JS chỉ xử lý hàng đợi sự kiện khi ngăn xếp thực thi trống. ii. Chuỗi phạm viĐể tìm một biến khi các chức năng đang chạy, JS trông xa hơn chỉ là môi trường biến của bối cảnh hiện đang thực hiện, nó cũng nhìn vào môi trường bên ngoài (môi trường mà chức năng này được đính kèm từ vựng). Quá trình này tiếp tục tìm kiếm tất cả các cách xuống môi trường toàn cầu trong một quy trình được gọi là chuỗi _Scope. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is7 iii. Đóng cửaMột trong những tính năng mạnh mẽ nhất của JS là đóng cửa. Bất cứ khi nào một hàm được lồng trong một hàm khác, hàm bên trong có quyền truy cập vào tất cả các biến của hàm bên ngoài ngay cả sau khi hàm bên ngoài thoát ra. Sau khi hàm bên ngoài thoát ra, nó sẽ xuất hiện khỏi ngăn xếp thực thi, tuy nhiên nếu bất kỳ biến nào của nó được tham chiếu trong hàm bên trong, thì các biến đó được "đóng vào" bối cảnh thực thi của hàm bên trong và có thể truy cập được bởi hàm bên trong.closures. Whenever a function is nested within another function, the inner function has access to all the outer function's variables even after the outer function exits. After the outer function exits, it is popped off the Execution Stack, however if any of its variables are referenced in the inner function, then those variables are "closed into" the inner function's Execution Context and are accessible by the inner function. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is8 iv. Gọi lạiGọi lại chỉ đơn giản là các hàm được truyền dưới dạng đối số cho các chức năng khác sẽ được chạy khi các chức năng khác kết thúc. are simply functions passed as arguments to other functions to be run when the other functions are finished. // JavaScript has one number type (which is a 64-bit IEEE 754 double). // Doubles have a 52-bit mantissa, which is enough to store integers // up to about 9✕10¹⁵ precisely. 3; // = 3 1.5; // = 1.5 // Some basic arithmetic works as you'd expect. 1 + 1; // = 2 0.1 + 0.2; // = 0.30000000000000004 (funky floating point arithmetic--be careful!) 8 - 1; // = 7 10 * 2; // = 20 10 ** 2; // =100 (10 raised to the power 2) same as Math.pow(10, 2) 35 / 5; // = 7 // Including uneven division. 5 / 2; // = 2.5 // Bitwise operations also work; when you perform a bitwise operation your float // is converted to a signed int *up to* 32 bits. 1 << 2; // = 4 // Precedence is enforced with parentheses. (1 + 3) * 2; // = 8 // There are special primitive values: Infinity; // result of e.g. 1/0 -Infinity; // result of e.g. -1/0 NaN; // result of e.g. 0/0 undefined; // never use this yourself. This is the default value for "not assigned" null; // use this instead. This is the programmer setting a var to "not assigned" // There's also a boolean type. true; false; // Strings are created with single quotes (') or double quotes ("). 'abc'; "Hello, world"; // You can access characters in a string with `charAt` "This is a string".charAt(0); // = 'T' // ...or use `substring` to get larger pieces. "Hello world".substring(0, 5); // = "Hello" "Hello world".slice(0, 5); // does the same thing "Hello world".substr(0, 5); // yet again // `length` is a property, so don't use (). "Hello".length; // = 5 // Searching strings "Mary had a little lamb".search("had"); // returns 5 "Mary had a little lamb".indexOf("zebra"); // returns -1 "Mary had a little lamb".includes("had"); //returns true (ES7). includes() will return true if the parameter provided is in the string, and false otherwise. // String to a character array "one two three four".split(" "); // ['one', 'two', 'three', 'four'] // String replace "happy birthday henry!".replace("h", "H"); // "Happy birthday Henry!" // ES6 also introduces Symbol as a new primitive type // But I'll add that on here once I actually figure out what it is9 5. JS định hướng đối tượng và kế thừa nguyên mẫutôi. Chất xây dựng chức năngKhi bạn gọi một hàm với từ khóa // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false7, một đối tượng mới được tạo trong bộ nhớ và được cung cấp cho hàm thông qua từ khóa // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2. Các chức năng được thiết kế để được gọi là như thế được gọi là các hàm tạo. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false0 ii. Nguyên mẫuMỗi đối tượng JavaScript có thuộc tính 'nguyên mẫu', chỉ đơn giản là tham chiếu đến một đối tượng khác. Khi bạn đi để truy cập một thuộc tính không tồn tại trên đối tượng thực tế, trình thông dịch sẽ xem xét nguyên mẫu của nó. Nếu nó không tồn tại trên nguyên mẫu, nó sẽ xem xét nguyên mẫu của nguyên mẫu. Nó sẽ tiếp tục nhìn xuống chuỗi nguyên mẫu này cho đến khi nó chạm vào đối tượng cơ sở, không có nguyên mẫu.prototype chain until it hits the base object Object, which doesn't have a prototype. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false1 iii. Kế thừa nguyên mẫu aka cài đặt nguyên mẫu của các đối tượng mớiTruy cập // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false9 là không chuẩn và không có cách nào tiêu chuẩn để thay đổi nguyên mẫu của một đối tượng hiện có. Tuy nhiên, có hai cách để tạo một đối tượng mới với một nguyên mẫu nhất định. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false2 Mỗi chức năng JS cũng có một thuộc tính gọi là 'nguyên mẫu'. Khi được sử dụng làm hàm bình thường, thuộc tính 'nguyên mẫu' không được sử dụng. Chỉ khi các hàm được sử dụng làm hàm tạo với từ khóa // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false7, 'nguyên mẫu' đặt nguyên mẫu của đối tượng được tạo. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false3 iv. Nhà xây dựng tích hợp// Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false4 Polyfilling tận dụng thực tế là chúng ta có thể sửa đổi các nguyên mẫu tích hợp để thực hiện các tính năng mới hơn của JavaScript trong một tập hợp con cũ của JavaScript, để chúng có thể được sử dụng trong các môi trường cũ như trình duyệt lỗi thời. takes advantage of the fact that we can modify the built-in prototypes to implement newer features of JavaScript in an older subset of JavaScript, so that they can be used in older environments such as outdated browsers. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false5 6. Lỗi và xử lý lỗi// Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false6 7. Công cụ ES6 mớiMũi tênMũi tên là một hàm đóng số cho các hàm ẩn danh được sử dụng với cú pháp // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }1. Họ chuyển phạm vi từ vựng bên ngoài (ví dụ: // Arrays are ordered lists of values, of any type. var myArray = ["Hello", 45, true]; // Their members can be accessed using the square-brackets subscript syntax. // Array indices start at zero. myArray[1]; // = 45 // Arrays are mutable and of variable length (dynamically sized arrays) myArray.push("World"); // adds to the end myArray.length; // = 4 // Add/Modify at specific index myArray[3] = "Hello"; //ES7 includes() can be used with arrays to check for the presence of a value. it is case sensitive let names = ["Samuel", "Hamilton", "Eric"]; names.includes("Samuel"); //true names.includes("samuel"); //false names.includes("John"); //false2) cho chức năng. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false7 Các lớp họcĐường cú pháp định hướng đối tượng cho mô hình di truyền nguyên mẫu. // Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false8 Chuỗi nội suy// Operators have both a precedence (order of importance, like * before +) // and an associativity (order of evaluation, like left-to-right) // A table of operators can be found here // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence) // Negation uses the ! symbol !true; // = false !false; // = true // There's shorthand operators for performing math operations on variables: someVar += 5; // equivalent to someVar = someVar + 5; someVar *= 10; // someVar = someVar * 10; // and an even-shorter-hand operators for adding or subtracting 1 someVar++; someVar--; // Strings are concatenated with + "Hello " + "world!"; // = "Hello world!" // Comparison Operators 1 < 10; // = true 1 > 10; // = false 2 <= 2; // = true 2 >= 2; // = true // and are compared with < and > "a" < "b"; // = true // Strict Equality is === // Strict meaning both type AND value are the same 1 === 1; // = true 2 === 1; // = false // Strict Inequality is !== 1 !== 1; // = false 2 !== 1; // = true // == allows for type coercion (conversion) and only checks if the values are equal after coercion "5" == 5; // = true null == undefined; // = true // ...which can result in some weird behaviour...so use === whenever possible 13 + !0; // 14 "13" + !0; // '13true' // false, null, undefined, NaN, 0 and "" are falsy; everything else is truthy. // Note that 0 is falsy and "0" is truthy, even though 0 == "0". // We can use this to our advantage when checking for existence if (x) { //doSomething }; // Or to set default values x = x || "default" // if x exists, do nothing and short-circuit, else set x to a default // but a problem arises if x = 0. It exists, but will coerce to false // be wary of this // figuring out types of literals and vars typeof "Hello"; // = "string" typeof 42; // = "number" typeof undefined // = "undefined" typeof null // = 'object' THIS IS A JS BUG! // figuring out if an object is an instance of another object // checks all the way down the prototype chain var x = {} x instanceof Object // = true x instanceof Function // = false9 // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }3 và // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }4// The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }3 giống như // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }6 ngoại trừ nó được phân tích khối. Các biến được khai báo với // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }4 chỉ có thể được chỉ định một lần. // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined0 Máy phát điệnCác chức năng có thể được tạm dừng bằng cách sử dụng từ khóa // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }8 và khởi động lại từ bên ngoài. // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }9 được gọi là "biểu thức năng suất" được đánh giá với bất kỳ giá trị nào chúng tôi gửi khi chúng tôi khởi động lại trình tạo. // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }8 đang thực hiện một yêu cầu cho một giá trị. // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined1 Máy phát điện rất hữu ích vì chúng quay lại (tức là tạo) iterators. Đổi lại, một trình lặp, một đối tượng có phương thức // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);1, thực sự thực hiện thân máy của các máy phát. Phương thức // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);1, khi được gọi nhiều lần, thực hiện một phần trình tạo tương ứng, dần dần tiến qua cơ thể cho đến khi từ khóa // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }8 bị nhấn. // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined2 Phương pháp // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);1 của một trình lặp trả về một đối tượng có thuộc tính // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);5 và thuộc tính // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);6, miễn là phần thân của trình tạo tương ứng chưa // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);7ed. Thuộc tính // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);5 đề cập đến giá trị // The `if` structure works as you'd expect. var count = 1; if (count === 3){ // evaluated if count is 3 } else if (count === 4){ // evaluated if count is 4 } else { // evaluated if it's not either 3 or 4 } // As does `while`. while (true){ // An infinite loop! } // Do-while loops are like while loops, except they always run at least once. var input; do { input = getInput(); } while (!isValid(input)) // The `for` loop is the same as C++ and Java: // initialisation; continue condition; iteration. for (var i = 0; i < 5; i++){ // will run 5 times } // && is logical AND, || is logical OR if (house.size === "big" && house.colour === "blue"){ house.contains = "bear"; } if (colour === "red" || colour === "blue"){ // colour is either red or blue } // The `switch` statement checks for equality with `===`. // use 'break' after each case // or the cases after the correct one will be executed too. grade = 'B'; switch (grade) { case 'A': console.log("Great job"); break; case 'B': console.log("OK job"); break; case 'C': console.log("You can do better"); break; default: console.log("Oy vey"); break; }8ed hoặc // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);7ed. Thuộc tính // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);6 là // JavaScript functions are declared with the `function` keyword. // This is a function statement function myFunction(thing){ return thing.toUpperCase(); } // This is a function expression var makeUpperCase = function() { return think.toUpperCase(); } // Note that the value to be returned must start on the same line as the // `return` keyword, otherwise you'll always return `undefined` due to // automatic semicolon insertion. Watch out for this when using Allman style. function myFunction() { return // <- semicolon automatically inserted here { thisIsAn: 'object literal' } } myFunction(); // = undefined // JavaScript functions are first class objects, so they can be reassigned to // different variable names and passed to other functions as arguments - for // example, when supplying an event handler: function myFunction(){ // this code will be called in 5 seconds' time } setTimeout(myFunction, 5000); // Note: setTimeout isn't part of the JS language, but is provided by browsers // and Node.js.2 cho đến khi thân máy phát // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);7, tại thời điểm đó là // JavaScript functions are declared with the `function` keyword. // This is a function statement function myFunction(thing){ return thing.toUpperCase(); } // This is a function expression var makeUpperCase = function() { return think.toUpperCase(); } // Note that the value to be returned must start on the same line as the // `return` keyword, otherwise you'll always return `undefined` due to // automatic semicolon insertion. Watch out for this when using Allman style. function myFunction() { return // <- semicolon automatically inserted here { thisIsAn: 'object literal' } } myFunction(); // = undefined // JavaScript functions are first class objects, so they can be reassigned to // different variable names and passed to other functions as arguments - for // example, when supplying an event handler: function myFunction(){ // this code will be called in 5 seconds' time } setTimeout(myFunction, 5000); // Note: setTimeout isn't part of the JS language, but is provided by browsers // and Node.js.4. Nếu phương thức // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);1 được gọi sau khi // They can be made literally: var myObj = {key1: "Hello", key2: "World"}; // or using the Object constructor: var myObj = new Object(); // Keys are strings, but quotes aren't required if they're a valid // JavaScript identifier. Values can be any type including other objects. var myObj = {myKey: "myValue", "my other key": 4}; // Objects can even contain functions (called methods) // When functions attached to an object are called, they can access the object // they're attached to using the `this` keyword. var myObj = { name: "Destiny's Child", sayMyName: function() { console.log(this.name); } } myObj.sayMyName(); // outputs "Destiny's Child" // Object attributes can also be accessed using the subscript syntax, myObj["my other key"]; // = 4 // ... or using the dot syntax, provided the key is a valid identifier. myObj.myKey; // = "myValue" // Objects are mutable; values can be changed and new keys added. myObj.myThirdKey = true; // If you try to access a value that's not yet set, you'll get undefined. myObj.myFourthKey; // = undefined // iterating through objects for(var property in myObj) { // do something } // JSON (JavaScript Object Notation) is just a special case of Object literal notation // where the keys are strings wrapped in quotes var json_stuff = { "firstName": "John", "lastName": "Doe", "Age": 25 } // JS Object => JSON JSON.stringify(myObj); // JSON => JS Object JSON.parse(json_stuff);6 là // JavaScript functions are declared with the `function` keyword. // This is a function statement function myFunction(thing){ return thing.toUpperCase(); } // This is a function expression var makeUpperCase = function() { return think.toUpperCase(); } // Note that the value to be returned must start on the same line as the // `return` keyword, otherwise you'll always return `undefined` due to // automatic semicolon insertion. Watch out for this when using Allman style. function myFunction() { return // <- semicolon automatically inserted here { thisIsAn: 'object literal' } } myFunction(); // = undefined // JavaScript functions are first class objects, so they can be reassigned to // different variable names and passed to other functions as arguments - for // example, when supplying an event handler: function myFunction(){ // this code will be called in 5 seconds' time } setTimeout(myFunction, 5000); // Note: setTimeout isn't part of the JS language, but is provided by browsers // and Node.js.4, một lỗi được ném. Bản đồ, bộ, yếu, yếuBản đồ là một đối tượng mà các phím có thể là bất kỳ đối tượng tùy ý nào. Một tập hợp là một cấu trúc dữ liệu chứa một tập hợp các phần tử hữu hạn, mỗi phần tử chỉ xảy ra một lần. Yếu và yếu cung cấp các bảng bên cạnh đối tượng không bị rò rỉ. Máy ảo JavaScript định kỳ giải phóng bộ nhớ được phân bổ cho các đối tượng không còn trong phạm vi. Một đối tượng không còn trong phạm vi nếu không có chuỗi tài liệu tham khảo từ phạm vi hiện tại dẫn đến nó. // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined3 Hứa hẹnLời hứa là một thư viện cho lập trình không đồng bộ. Lời hứa là một đại diện hạng nhất của một giá trị có thể được cung cấp trong tương lai. Một lời hứa là ở một trong những trạng thái này:
// Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined4 Mô -đun// Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined5 // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined6 // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined7 Ủy quyềnĐối tượng proxy được sử dụng để xác định hành vi tùy chỉnh cho các hoạt động cơ bản (ví dụ: tra cứu thuộc tính, gán, liệt kê, gọi chức năng, v.v.). // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined8 // Variables are declared with the `var` keyword. JavaScript is dynamically // typed, so you don't need to specify type. Assignment uses a single `=` // character. var someVar = 5; // if you leave the var keyword off, you won't get an error... someOtherVar = 10; // ...but your variable will be created in the global scope, not in the scope // you defined it in. // Variables declared without being assigned to are set to undefined. var someThirdVar; // = undefined9 TODO: Biểu tượng |
