Straight-forward string.prototype format method for Javascript.

string.prototype.format.js

// Credit: http://joquery.com/2012/string-format-for-javascript
String.prototype.format = function() {
	var s = this;
	for (var i = 0; i < arguments.length; i++) {       
		var reg = new RegExp("\\{" + i + "\\}", "gm");             
		s = s.replace(reg, arguments[i]);
	}
	return s;
}