PHP number_format in Javascript

gistfile1.js

//UK format - commas for thousands separator, full stop for decimal.
//d = number of decimal points.

String.prototype.number_format = function(d) {
    var n = this;
    var c = isNaN(d = Math.abs(d)) ? 2 : d;
    var s = n < 0 ? "-" : "";
    var i = parseInt(n = Math.abs(+n || 0).toFixed(c)) + "", j = (j = i.length) > 3 ? j % 3 : 0;
    return s + (j ? i.substr(0, j) + ',' : "") + i.substr(j).replace(/(\d{3})(?=\d)/g, "$1" + ',') + (c ? '.' + Math.abs(n - i).toFixed(c).slice(2) : "");
}

console.log(
'2234324.99'.number_format()
);

//2,234,324.99