JavaScript numbers to Words

Question

I\'m trying to convert numbers into english words, for example 1234 would become: \"one thousand two hundred thirty four\".

My Tact

Answer 1

If anybody ever wants to do this but in Spanish (en español), here's my code based on Hardik's

function num2str(num, moneda) {
    moneda = moneda || (num !== 1 ? "pesos" : "peso");
    var fraction = Math.round(__cf_frac(num) * 100);
    var f_text = " (" + pad(fraction, 2) + "/100 M.N.)";


    return __cf_convert_number(num) + " " + moneda + f_text;
}

function __cf_frac(f) {
    return f % 1;
}

function __cf_convert_number(number) {
    if ((number < 0) || (number > 999999999)) {
        throw Error("N\u00famero fuera de rango");
    }
    var millon = Math.floor(number / 1000000);
    number -= millon * 1000000;
    var cientosDeMiles = Math.floor(number / 100000);
    number -= cientosDeMiles * 100000;
    var miles = Math.floor(number / 1000);
    number -= miles * 1000;
    var centenas = Math.floor(number / 100);
    number = number % 100;
    var tn = Math.floor(number / 10);
    var one = Math.floor(number % 10);
    var res = "";

    var cientos = Array("", "cien", "doscientos", "trescientos", "cuatrocientos", "quinientos", "seiscientos", "setecientos", "ochocientos", "novecientos");
    if (millon > 0) {
        res += (__cf_convert_number(millon) + (millon === 1 ? " mill\u00f3n" : " millones"));
    }
    if (cientosDeMiles > 0) {
        res += (((res == "") ? "" : " ") +
            cientos[cientosDeMiles] + (miles > 0 || centenas > 0 || tn > 0 || one < 0 ? (cientosDeMiles == 1 ? "to " : " ") : ""));
    }
    if (miles > 0) {
        res += (((res == "") ? "" : " ") +
            __cf_convert_number(miles) + " mil");
    }
    if (centenas) {
        res += (((res == "") ? "" : " ") +
            cientos[centenas] + (tn > 0 || one > 0 ? (centenas > 1 ? " " : "to ") : ""));
    }


    var ones = Array("", "un", "dos", "tres", "cuatro", "cinco", "seis", "siete", "ocho", "nueve", "diez", "once", "doce", "trece", "catorce", "quince", "dieciseis", "diecisiete", "dieciocho", "diecinueve");
    var tens = Array("", "", "veinte", "treinta", "cuarenta", "cincuenta", "sesenta", "setenta", "ochenta", "noventa");

    if (tn > 0 || one > 0) {
        if (tn < 2) {
            res += ones[tn * 10 + one];
        }
        else {
            if (tn === 2 && one > 0)
                res += "veinti" + ones[one];
            else {
                res += tens[tn];
                if (one > 0) {
                    res += (" y " + ones[one]);
                }
            }
        }
    }

    if (res == "") {
        res = "cero";
    }
    return res.replace("  ", " ");
}

function pad(num, largo, char) {
    char = char || '0';
    num = num + '';
    return num.length >= largo ? num : new Array(largo - num.length + 1).join(char) + num;
}

Result:

num2str(123456789)
"ciento veintitres millones cuatrocientos cincuenta y seis mil setecientos ochenta y nueve pesos (00/100 M.N.)"