angularjs string format

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;
}

var a = "this is {0} test for {1}{2}";
alert(String.format(a, "a","me"."!"));