javascript function that helps convert javascript number into a nice format with the function niceFormat for thousand separator, negative uses () etc

stringformat.js

if (!Number.prototype.niceFormat) {
    Number.prototype.niceFormat = function(options) {
        var defaultOptions = {
            thousandSeparator: ',',
            leftPad: 0,
            decimalPlaces: 2,
            negative: '()'
        };
        var env = defaultOptions;
        if (typeof options != 'undefined') {
            for (option in env) {
                if (options.hasOwnProperty(option)
                && typeof options[option] != 'undefined') {
                        env[option] = options[option];
                }
            }
        }

        if (env.thousandSeparator == false) {
            env.thousandSeparator = '';
        }

        var number       = this.toFixed(env.decimalPlaces + 1).toString();
        var simpleNumber = '';

        // Strips out the dollar sign and commas.
        for (var i = 0; i < number.length; ++i)
        {
            if ("0123456789.".indexOf(number.charAt(i)) >= 0)
                simpleNumber += number.charAt(i);
        }

        number = parseFloat(simpleNumber);

        if (isNaN(number)) {
            number = 0;
        }
        if (env.leftPad == 0) {
            env.leftPad = 1;
        }

        var integerPart = (env.decimalPlaces > 0 ? Math.floor(number) : Math.round(number));
        var string      = "";

        for (var i = 0; i < env.leftPad || integerPart > 0; ++i)
        {
            // Insert a comma every three digits.
            if (env.thousandSeparator.length > 0 && string.match(/^\d\d\d/))
                string = env.thousandSeparator + string;

            string      = (integerPart % 10) + string;
            integerPart = Math.floor(integerPart / 10);
        }

        if (env.decimalPlaces > 0)
        {
            number -= Math.floor(number);
            number *= Math.pow(10, env.decimalPlaces);

            string += "." + number.niceFormat({leftPad: env.decimalPlaces, decimalPlaces: 0, thousandSeparator:false});
        }

        if (this < 0) {
            if (env.negative == '()') {
                string = '(' + string + ')';
            } else {
                string = env.negative + string;
            }
        }
        return string;
    };
}