word-number-word/dist/numberToWord.js

A TypeScript/JavaScript utility for converting numbers to words and vice versa — including support for decimals, negatives, and currency converting.

const UNITS = [
    "zero",
    "one",
    "two",
    "three",
    "four",
    "five",
    "six",
    "seven",
    "eight",
    "nine",
];
const TEENS = [
    "ten",
    "eleven",
    "twelve",
    "thirteen",
    "fourteen",
    "fifteen",
    "sixteen",
    "seventeen",
    "eighteen",
    "nineteen",
];
const TENS = [
    "",
    "ten",
    "twenty",
    "thirty",
    "forty",
    "fifty",
    "sixty",
    "seventy",
    "eighty",
    "ninety",
];
const SCALES = [
    "",
    "thousand",
    "million",
    "billion",
    "trillion",
    "quadrillion",
];
export function numberToWord(num) {
    // Convert string input to number (e.g., "4.55" → 4.55)
    const parsedNum = typeof num === "string" ? parseFloat(num) : num;
    // Validate input
    if (isNaN(parsedNum)) {
        throw new Error("Input must be a valid number");
    }
    // Check for more than 2 decimal places
    const decimalPart = parsedNum.toString().split(".")[1];
    if (decimalPart && decimalPart.length > 2) {
        throw new Error("Maximum 2 decimal places allowed");
    }
    // Handle negative numbers
    if (parsedNum < 0) {
        return "minus " + numberToWord(Math.abs(parsedNum));
    }
    // Split into integer and decimal parts
    const integerPart = Math.floor(parsedNum);
    const decimalValue = Math.round((parsedNum - integerPart) * 100);
    // Convert integer part
    let result = convertInteger(integerPart);
    // Convert decimal part (if exists)
    if (decimalValue > 0) {
        result += " point " + convertInteger(decimalValue);
    }
    return result;
}
function convertInteger(num) {
    if (num < 20)
        return num < 10 ? UNITS[num] : TEENS[num - 10];
    if (num < 100) {
        const ten = Math.floor(num / 10);
        const unit = num % 10;
        return TENS[ten] + (unit ? "-" + UNITS[unit] : "");
    }
    if (num < 1000) {
        const hundred = Math.floor(num / 100);
        const remainder = num % 100;
        return (UNITS[hundred] +
            " hundred" +
            (remainder ? " and " + convertInteger(remainder) : ""));
    }
    for (let i = 0; i < SCALES.length; i++) {
        const scaleValue = Math.pow(1000, i + 1);
        if (num < scaleValue) {
            const scaleNum = Math.floor(num / (scaleValue / 1000));
            const remainder = num % (scaleValue / 1000);
            return (convertInteger(scaleNum) +
                " " +
                SCALES[i] +
                (remainder
                    ? (remainder < 100 ? " and " : " ") + convertInteger(remainder)
                    : ""));
        }
    }
    return "number too large";
}