Top 10 String Javascript Interview Coding Question

1. Reverse a String

function reverseString(str) {
    return str.split('').reverse().join('');
}
console.log(reverseString("hello")); // Output: "olleh"

2. How to check the name of the number in English?

function numberToWords(number) {
    const singleDigits = ['', 'one', 'two', 'three', 'four', 'five', 'six', 'seven', 'eight', 'nine'];
    const teens = ['ten', 'eleven', 'twelve', 'thirteen', 'fourteen', 'fifteen', 'sixteen', 'seventeen', 'eighteen', 'nineteen'];
    const tens = ['', '', 'twenty', 'thirty', 'forty', 'fifty', 'sixty', 'seventy', 'eighty', 'ninety'];

    if (number === 0) {
        return 'zero';
    }

    if (number < 10) {
        return singleDigits[number];
    }

    if (number < 20) {
        return teens[number - 10];
    }

    if (number < 100) {
        return tens[Math.floor(number / 10)] + ' ' + singleDigits[number % 10];
    }

    if (number < 1000) {
        return singleDigits[Math.floor(number / 100)] + ' hundred ' + numberToWords(number % 100);
    }

    if (number < 1000000) {
        return numberToWords(Math.floor(number / 1000)) + ' thousand ' + numberToWords(number % 1000);
    }

    if (number < 1000000000) {
        return numberToWords(Math.floor(number / 1000000)) + ' million ' + numberToWords(number % 1000000);
    }

    return 'Number too large to convert';
}

// Example usage:
console.log(numberToWords(123)); // Outputs: ""one hundred twenty three""
console.log(numberToWords(12345)); // Outputs: ""twelve thousand three hundred forty five""
console.log(numberToWords(123456789)); // Outputs: ""one hundred twenty three million four hundred fifty six thousand seven hundred eighty nine"""

*3. How to calculate the number of vowels and consonants in a string?
*

function countVowelsAndConsonants(str: string): { vowels: number, consonants: number } {
    // Define a regular expression to match vowels (case-insensitive)
    const vowelRegex = /[aeiou]/i;

    let vowels = 0;
    let consonants = 0;

    // Convert the string to lowercase for case-insensitive comparison
    const lowerCaseStr = str.toLowerCase();

    // Iterate through each character of the string
    for (let char of lowerCaseStr) {
        // Check if the character is a letter
        if (/[a-z]/i.test(char)) {
            // Increment the count of vowels if the character is a vowel
            if (vowelRegex.test(char)) {
                vowels++;
            } else {
                // Increment the count of consonants if the character is a consonant
                consonants++;
            }
        }
    }

    // Return the count of vowels and consonants
    return { vowels, consonants };
}

// Example usage:
const inputString = ""Hello World"";
const { vowels, consonants } = countVowelsAndConsonants(inputString);
console.log(""Vowels:"", vowels); // Output: 3
console.log(""Consonants:"", consonants); // Output: 7

4. how to calculate 2 largest vowel count from string

function calculateTwoLargestVowelCounts(str: string): number[] {
    // Define an array to store counts of each vowel (a, e, i, o, u)
    const vowelCounts: number[] = [0, 0, 0, 0, 0];

    // Convert the string to lowercase for case-insensitive comparison
    const lowerCaseStr = str.toLowerCase();

    // Iterate through each character of the string
    for (let char of lowerCaseStr) {
        // Check if the character is a vowel
        switch (char) {
            case 'a':
                vowelCounts[0]++;
                break;
            case 'e':
                vowelCounts[1]++;
                break;
            case 'i':
                vowelCounts[2]++;
                break;
            case 'o':
                vowelCounts[3]++;
                break;
            case 'u':
                vowelCounts[4]++;
                break;
        }
    }

    // Sort the array in descending order to find the two largest counts
    const sortedCounts = vowelCounts.slice().sort((a, b) => b - a);

    // Return the two largest counts
    return sortedCounts.slice(0, 2);
}

// Example usage:
const inputString = ""Hello World"";
const twoLargestCounts = calculateTwoLargestVowelCounts(inputString);
console.log(""Two Largest Vowel Counts:"", twoLargestCounts); // Output: [2, 1]