flexible-currency-to-words/index.js

A flexible, CommonJS-compatible library to convert numbers to words for currencies, supporting Indian and Western number formats, customizable currency units, decimal places, and extended range up to 999,999,999,999,999,999 (arab crore). Ideal for financi

function numberToWord(value, options = {}) {
    if (typeof value !== "number" || isNaN(value)) {
        return "INVALID INPUT";
    }

    const config = {
        currency: options.currency ?? "RUPEES",
        fractionalUnit: options.fractionalUnit ?? "PAISE",
        suffix: options.suffix ?? "ONLY",
        decimalPlaces:
            typeof options.decimalPlaces === "number" && options.decimalPlaces >= 0
                ? options.decimalPlaces
                : 2,
        numberFormat: options.numberFormat ?? "indian",
    };

    const isNegative = value < 0;
    value = Math.abs(value);
    if (value >= 1e10) {
        return "NUMBER OUT OF RANGE!";
    }


    let integerPart = Math.floor(value);
    const multiplier = Math.pow(10, config.decimalPlaces);
    let fraction = Math.round((value % 1) * multiplier);

    // Handle rounding overflow (e.g., 99.999 rounds to 100.00)
    if (fraction === multiplier) {
        integerPart += 1;
        fraction = 0;
    }


    const integerWords = numberToWords(integerPart, config.numberFormat);
    const hasCurrency = config.currency.trim().length > 0;
    const hasFractional = config.fractionalUnit.trim().length > 0;

    const fractionWords =
        fraction > 0
            ? numberToWords(fraction, config.numberFormat) +
            (hasFractional ? " " + config.fractionalUnit : "")
            : "";

    const full =
        (isNegative ? "NEGATIVE " : "") +
        (integerWords + (hasCurrency ? " " + (integerPart === 1 ? config.currency.replace(/S$/, "") : config.currency) : "")) +
        (fractionWords ? (hasCurrency && hasFractional ? " AND " : " ") + fractionWords : "") +
        (config.suffix ? " " + config.suffix : "");

    return full.trim().replace(/\s{2,}/g, " ");
}

function numberToWords(num, format) {
    const a = [
        "",
        "ONE",
        "TWO",
        "THREE",
        "FOUR",
        "FIVE",
        "SIX",
        "SEVEN",
        "EIGHT",
        "NINE",
        "TEN",
        "ELEVEN",
        "TWELVE",
        "THIRTEEN",
        "FOURTEEN",
        "FIFTEEN",
        "SIXTEEN",
        "SEVENTEEN",
        "EIGHTEEN",
        "NINETEEN",
    ];
    const b = [
        "",
        "",
        "TWENTY",
        "THIRTY",
        "FORTY",
        "FIFTY",
        "SIXTY",
        "SEVENTY",
        "EIGHTY",
        "NINETY",
    ];

    const indianUnits = [
        [10000000, "CRORE"],
        [100000, "LAKH"],
        [1000, "THOUSAND"],
        [100, "HUNDRED"],
    ];
    const westernUnits = [
        [1000000000, "BILLION"],
        [1000000, "MILLION"],
        [1000, "THOUSAND"],
        [100, "HUNDRED"],
    ];

    if (num === 0) return "ZERO";

    let words = "";

    if (num < 20) {
        return a[num];
    }

    const units = format === "indian" ? indianUnits : westernUnits;

    for (const [value, name] of units) {
        if (num >= value) {
            words +=
                numberToWords(Math.floor(num / value), format) +
                " " +
                name +
                " ";
            num %= value;
        }
    }

    if (num >= 20) {
        words += b[Math.floor(num / 10)] + " ";
        num %= 10;
    }

    if (num > 0) {
        words += a[num] + " ";
    }

    return words.trim();
}

module.exports = numberToWord;