String format implementation with padding.

String.format.js

String.prototype.format = String.prototype.f = function () {
    var s = this;
	for (var i = 0; i < arguments.length; i++) {
		var m = s.match("\\{(" + i + ")(:.*?)?\\}", "gm");
		if (m) {
			if (m[2]) {
				var x = m[2].substring(1);
				if (x.search("^(.)\\1+$") > -1) {
					var p = arguments[parseInt(m[1], 10)].toString();
					while (p.length < x.length) {
						p = x.substring(0, 1) + p.toString();
					}
					s = s.replace(m[0], p);
				}
			} else {
				s = s.replace(m[0], arguments[parseInt(m[1], 10)]);
			}
		}
	}
	return s.toString();
};