Is there a vowel in there javascript?

The five letters a, e, i, o and u are called vowels. All other alphabets except these 5 vowels are called consonants.

Example 1: Count the Number of Vowels Using Regex

// program to count the number of vowels in a string

function countVowel(str) { 

    // find the count of vowels
    const count = str.match(/[aeiou]/gi).length;

    // return number of vowels
    return count;
}

// take input
const string = prompt('Enter a string: ');

const result = countVowel(string);

console.log(result);

Output

Enter a string: JavaScript program
5

In the above program, the user is prompted to enter a string and that string is passed to the countVowel() function.

• The regular expression (RegEx) pattern is used with the match() method to find the number of vowels in a string.
• The pattern /[aeiou]/gi checks for all the vowels (case-insensitive) in a string. Here,
  str.match(/[aeiou]/gi); gives ["a", "a", "i", "o", "a"]
• The length property gives the number of vowels present.

Example 2: Count the Number of Vowels Using for Loop

// program to count the number of vowels in a string

// defining vowels
const vowels = ["a", "e", "i", "o", "u"]

function countVowel(str) {
    // initialize count
    let count = 0;

    // loop through string to test if each character is a vowel
    for (let letter of str.toLowerCase()) {
        if (vowels.includes(letter)) {
            count++;
        }
    }

    // return number of vowels
    return count
}

// take input
const string = prompt('Enter a string: ');

const result = countVowel(string);

console.log(result);

Output

Enter a string: JavaScript program
5

In the above example,

• All the vowels are stored in a vowels array.
• Initially, the value of the count variable is 0.
• The for...of loop is used to iterate over all the characters of the string.
• The toLowerCase() method converts all the characters of a string to lowercase.
• The includes() method checks if the vowel array contains any of the characters of the string.
• If any character matches, the value of count is increased by 1.

I'm supposed to write a function that takes a character (i.e. a string of length 1) and returns true if it is a vowel, false otherwise. I came up with two functions, but don't know which one is better performing and which way I should prefer. The one with RegEx is way simpler but I am unsure whether I should try to avoid using RegEx or not?

Without RegEx:

function isVowel(char) {
  if (char.length == 1) {
    var vowels = new Array("a", "e", "i", "o", "u");
    var isVowel = false;

    for (e in vowels) {
      if (vowels[e] == char) {
        isVowel = true;
      }
    }

    return isVowel;
  }
}

With RegEx:

function isVowelRegEx(char) {
  if (char.length == 1) {
    return /[aeiou]/.test(char);
  }
}

Penny Liu

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asked Mar 30, 2011 at 14:55

3

benchmark

I think you can safely say a for loop is faster.

I do admit that a regexp looks cleaner in terms of code. If it's a real bottleneck then use a for loop, otherwise stick with the regular expression for reasons of "elegance"

If you want to go for simplicity then just use

function isVowel(c) {
    return ['a', 'e', 'i', 'o', 'u'].indexOf(c.toLowerCase()) !== -1
}

answered Mar 30, 2011 at 15:01

RaynosRaynos

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7

Lots of answers available, speed is irrelevant for such small functions unless you are calling them a few hundred thousand times in a short period of time. For me, a regular expression is best, but keep it in a closure so you don't build it every time:

Simple version:

function vowelTest(s) {
  return (/^[aeiou]$/i).test(s);
}

More efficient version:

var vowelTest = (function() {
  var re = /^[aeiou]$/i;
  return function(s) {
    return re.test(s);
  }
})();

Returns true if s is a single vowel (upper or lower case) and false for everything else.

answered Mar 30, 2011 at 23:39

RobGRobG

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4

cycles, arrays, regexp... for what? It can be much quicker :)

function isVowel(char)
{
    return char === 'a' || char === 'e' || char === 'i' || char === 'o' || char === 'u' || false;
}

answered Mar 30, 2011 at 15:14

EmmermanEmmerman

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7

function findVowels(str) {
  return str.match(/[aeiou]/ig);
}

findVowels('abracadabra'); // 'aaaaa'

Basically it returns all the vowels in a given string.

answered Jun 10, 2017 at 15:01

This is a rough RegExp function I would have come up with (it's untested)

function isVowel(char) {
    return /^[aeiou]$/.test(char.toLowerCase());
}

Which means, if (char.length == 1 && 'aeiou' is contained in char.toLowerCase()) then return true.

answered Mar 30, 2011 at 15:05

Buhake SindiBuhake Sindi

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Personally, I would define it this way:

function isVowel( chr ){ return 'aeiou'.indexOf( chr[0].toLowerCase() ) !== -1 }

You could also use ['a','e','i','o','u'] and skip the length test, but then you are creating an array each time you call the function. (There are ways of mimicking this via closures, but those are a bit obscure to read)

bpierre

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answered Mar 30, 2011 at 15:01

cwallenpoolecwallenpoole

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1

I kind of like this method which I think covers all the bases:

const matches = str.match(/[aeiou]/gi);
return matches ? matches.length : 0;

answered Apr 8, 2019 at 11:16

IntellidroidIntellidroid

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1

function isVowel(char)
{
  if (char.length == 1)
  {
    var vowels = "aeiou";
    var isVowel = vowels.indexOf(char) >= 0 ? true : false;

    return isVowel;
  }
}

Basically it checks for the index of the character in the string of vowels. If it is a consonant, and not in the string, indexOf will return -1.

answered Mar 30, 2011 at 15:00

HåvardHåvard

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2

I created a simplified version using Array.prototype.includes(). My technique is similar to @Kunle Babatunde.

const isVowel = (char) => ["a", "e", "i", "o", "u"].includes(char);

console.log(isVowel("o"), isVowel("s"));

answered May 17, 2020 at 13:34

Penny LiuPenny Liu

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This is the way I did it, on the first occurrence of a vowel in any given word it breaks out of the loop and returns true.

const vowels = ["a", "e", "i", "o", "u", "y"];

function isVowel(word) {
    let result = false;
    for (let i = 0; i < word.length; i++) {
        if (vowels.includes(word[i])) {
            result = true;
            break;
        }
    }
    return result;

answered Apr 23, 2021 at 14:01

YuniacYuniac

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1

Basically it returns all the vowels in a given string.

function vowels(s) {
  let vowels = ["a", "e", "i", "o", "u"];

  for(let v of s) {
    if(vowels.includes(v))
        console.log(v);
  }
}

answered Aug 25, 2021 at 5:58

  //function to find vowel
const vowel = (str)=>{
  //these are vowels we want to check for
  const check = ['a','e','i','o','u'];
  //keep track of vowels
  var count = 0;
  for(let char of str.toLowerCase())
  {
    //check if each character in string is in vowel array
    if(check.includes(char)) count++;
  }
  return count;
}

console.log(vowel("hello there"));

answered Jun 13, 2018 at 17:31

1

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