Counting occurrences of vowel, consonants - JavaScript

We are required to write a JavaScript function that takes in a string which contains English alphabet, for example ?

const str = 'This is a sample string, will be used to collect some data';

The function should return an object containing the count of vowels and consonants in the string i.e. the output should be ?

{ vowels: 17, consonants: 29 }

Understanding the Problem

To count vowels and consonants, we need to:

• Iterate through each character in the string
• Check if the character is a letter (not a space or punctuation)
• Determine if it's a vowel (a, e, i, o, u) or consonant
• Keep count of both types

Solution Using reduce()

The most efficient approach uses the reduce() method to accumulate the counts:

const str = 'This is a sample string, will be used to collect some data';

const countAlpha = str => {
    return str.split('').reduce((acc, val) => {
        const legend = 'aeiou';
        let { vowels, consonants } = acc;
        
        // Skip non-alphabetic characters
        if(val.toLowerCase() === val.toUpperCase()){
            return acc;
        };
        
        // Check if vowel or consonant
        if(legend.includes(val.toLowerCase())){
            vowels++;
        } else {
            consonants++;
        };
        
        return { vowels, consonants };
    }, {
        vowels: 0,
        consonants: 0
    });
};

console.log(countAlpha(str));

{ vowels: 17, consonants: 29 }

Alternative Solution Using for...of Loop

Here's a more straightforward approach using a for...of loop:

function countVowelsConsonants(str) {
    const vowels = 'aeiouAEIOU';
    let vowelCount = 0;
    let consonantCount = 0;
    
    for (let char of str) {
        if (char.match(/[a-zA-Z]/)) {  // Only count letters
            if (vowels.includes(char)) {
                vowelCount++;
            } else {
                consonantCount++;
            }
        }
    }
    
    return { vowels: vowelCount, consonants: consonantCount };
}

const testString = 'Hello World! 123';
console.log(countVowelsConsonants(testString));

{ vowels: 3, consonants: 7 }

How It Works

The solution works by:

1. Character filtering: The condition val.toLowerCase() === val.toUpperCase() identifies non-letters (spaces, numbers, punctuation)
2. Vowel detection: Uses includes() to check if the lowercase character exists in the vowels string
3. Accumulation: The reduce() method maintains running counts in an accumulator object

Comparison of Methods

Conclusion

Both approaches effectively count vowels and consonants by filtering non-alphabetic characters and categorizing letters. The for...of loop is more readable, while reduce() offers a functional programming approach.