Can you have variables in javascript?
4 Ways to Declare a JavaScript Variable:
Show
What are Variables?Variables are containers for storing data (storing data values). In this example, In this example, In this
example, From all the examples above, you can guess:
When to Use JavaScript var?Always declare JavaScript variables with The The If
you want your code to run in older browsers, you must use When to Use JavaScript const?If you want a general rule: always declare variables with If you think the value of the variable can change, use In this example, Example const price1 = 5; Try it Yourself » The two variables These are constant values and cannot be changed. The variable This is a value that can be changed. Just Like AlgebraJust like in algebra, variables hold values: Just like in algebra, variables are used in expressions: From the example above, you can guess that the total is calculated to be 11. NoteVariables are containers for storing values. JavaScript IdentifiersAll JavaScript variables must be identified with unique names. These unique names are called identifiers. Identifiers can be short names (like x and y) or more descriptive names (age, sum, totalVolume). The general rules for constructing names for variables (unique identifiers) are:
NoteJavaScript identifiers are case-sensitive. The Assignment OperatorIn JavaScript, the equal sign ( This is different from algebra. The following does not make sense in algebra: In JavaScript, however, it makes perfect sense: it assigns the value of x + 5 to x. (It calculates the value of x + 5 and puts the result into x. The value of x is incremented by 5.) NoteThe "equal to" operator is
written like JavaScript Data TypesJavaScript variables can hold numbers like 100 and text values like "John Doe". In programming, text values are called text strings. JavaScript can handle many types of data, but for now, just think of numbers and strings. Strings are written inside double or single quotes. Numbers are written without quotes. If you put a number in quotes, it will be treated as a text string. Example const pi = 3.14; Try it Yourself » Declaring a JavaScript VariableCreating a variable in JavaScript is called "declaring" a variable. You declare a JavaScript variable with the var carName; or: let carName; After the
declaration, the variable has no value (technically it is To assign a value to the variable, use the equal sign: You can also assign a value to the variable when you declare it: In the example below, we create a variable called Then we "output" the value inside an HTML paragraph with id="demo": ExampleTry it Yourself » NoteIt's a good programming practice to declare all variables at the beginning of a script. One Statement, Many VariablesYou can declare many variables in one statement. Start the statement with A declaration can span multiple lines: Value = undefinedIn computer programs, variables are often declared without a value. The value can be something that has to be calculated, or something that will be provided later, like user input. A variable declared without a value will have the value The variable carName will have the value Re-Declaring JavaScript VariablesIf you re-declare a JavaScript variable declared with The variable NoteYou cannot re-declare a variable declared with This will not work: let carName = "Volvo"; JavaScript ArithmeticAs with algebra, you can do arithmetic with JavaScript
variables, using operators like You can also add strings, but strings will be concatenated: Also try this: NoteIf you put a number in quotes, the rest of the numbers will be treated as strings, and concatenated. Now try this: JavaScript Dollar Sign $Since JavaScript treats a dollar sign as a letter, identifiers containing $ are valid variable names: Using the dollar sign is not very common in JavaScript, but professional programmers often use it as an alias for the main function in a JavaScript library. In the JavaScript library jQuery, for instance, the main function JavaScript Underscore (_)Since JavaScript treats underscore as a letter, identifiers containing _ are valid variable names: Using the underscore is not very common in JavaScript, but a convention among professional programmers is to use it as an alias for "private (hidden)" variables. Are there variables in JavaScript?JavaScript variables can hold numbers like 100 and text values like "John Doe". In programming, text values are called text strings. JavaScript can handle many types of data, but for now, just think of numbers and strings.
Can you add variables in JavaScript?Unlike strongly typed programming languages such as C#, JavaScript is loosely typed and allows you to assign any data type to a variable without giving the variable a specific type. In JavaScript, for example, you can assign a number to a variable named "x" as easily as you can assign the word "apple" to it.
How many variables can you have in JavaScript?In JavaScript, there are three different variable types: var , let , and const . Each of these variables have several rules around how they should be used, and have different characteristics.
What variable names are not allowed in JavaScript?Rules for Naming Variables
The rest of the variable name can include any letter, any number, or the underscore. You can't use any other characters, including spaces, symbols, and punctuation marks. As with the rest of JavaScript, variable names are case sensitive.
|