String.format function in Javascript

Javascript String Formatting function (just like in C#);

String.format = function() {
    if(arguments.length == 0)
        return null;
        var str = arguments[0];
        for(var i=1;i<arguments.length;i++) {
            var re = new RegExp('\\{' + (i-1) + '\\}','gm');
            str = str.replace(re, arguments[i]);
        }
        return str;
}
////Sample;
//var a = String.format("{0} {1}", "Hello", "World");
////Output: Hello World