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 thevowel
array contains any of the characters of the string. - If any character matches, the value of
count
is increased by 1.
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