Integer to English Words

numberToWords.js

var numberToWords = function (num) {
    if (num === 0) return 'Zero';

    const units = ['', 'One', 'Two', 'Three', 'Four', 'Five', 'Six', 'Seven', 'Eight', 'Nine', 'Ten', 'Eleven', 'Twelve', 'Thirteen', 'Fourteen', 'Fifteen', 'Sixteen', 'Seventeen', 'Eighteen', 'Nineteen'];
    const tens = ['', '', 'Twenty', 'Thirty', 'Forty', 'Fifty', 'Sixty', 'Seventy', 'Eighty', 'Ninety'];
    const thousands = ['', 'Thousand', 'Million', 'Billion'];

    const helper = (num) => {
        if (num === 0) return '';
        if (num < 20) return `${units[num]} `;
        if (num < 100) return `${tens[parseInt(num / 10)]} ${helper(num % 10)}`;
        return `${units[parseInt(num / 100)]} Hundred ${helper(num % 100)}`;
    }

    let result = '';
    for (let i = 0; i < thousands.length; i++) {
        if (num % 1000 !== 0) result = `${helper(num % 1000)}${thousands[i]} ${result}`;
        num = parseInt(num / 1000);
    }
    return result.trim();
};

console.log(numberToWords(2147483647));

Convert a non-negative integer num to its English words representation.