Number of vowels within an array in JavaScript

We are required to write a JavaScript function that takes in an array of strings, (they may be a single character or greater than that). Our function should simply count all the vowels contained in the array.

Example

Let us write the code −

const arr = ['Amy','Dolly','Jason','Madison','Patricia'];
const countVowels = (arr = []) => {
   const legend = 'aeiou';
   const isVowel = c => legend.includes(c.toLowerCase());
   let count = 0;
   arr.forEach(el => {
      for(let i = 0; i < el.length; i++){
         if(isVowel(el[i])){
            count++;
         };
      };
   });
   return count;
};
console.log(countVowels(arr));

Output

And the output in the console will be −

10

Method 2: Using Regular Expressions

We can also use regular expressions to match vowels more efficiently:

const arr = ['Amy','Dolly','Jason','Madison','Patricia'];
const countVowelsRegex = (arr = []) => {
   const vowelPattern = /[aeiou]/gi;
   let count = 0;
   arr.forEach(str => {
      const matches = str.match(vowelPattern);
      if(matches) {
         count += matches.length;
      }
   });
   return count;
};
console.log(countVowelsRegex(arr));

10

Method 3: Using Reduce and Filter

A more functional programming approach using reduce and filter:

const arr = ['Amy','Dolly','Jason','Madison','Patricia'];
const countVowelsFunctional = (arr = []) => {
   const vowels = 'aeiou';
   return arr.reduce((total, str) => {
      return total + str.toLowerCase()
                        .split('')
                        .filter(char => vowels.includes(char))
                        .length;
   }, 0);
};
console.log(countVowelsFunctional(arr));

10

Comparison

Conclusion

All three methods effectively count vowels in an array of strings. The loop method is most readable for beginners, while regex offers better performance for large datasets.