String.format extension for JavaScript

string.format.js

/*
String.format extension for JavaScript

Next line should give you an idea how to use it:
"{1}, {0}!".format("world", "Hello");
*/

String.prototype.format = function() {
  var formatted = this;
  for (arg in arguments) {
    formatted = formatted.replace("{" + arg + "}", arguments[arg]);
  }
  return formatted;
};