ES6 Everyday: Rest Parameters

With ES6, you can now provide a rest parameter to a function that takes a variable amount of parameters and passes them as an array to a function. First thing I thought of creating with this was a simple string formatting function:

function formatString(input, ...args)
  var output = input;
  for(var i=0; i<args.length; i++) {
    output = output.replace(new RegExp("\\{" + i + "\\}", "g"), args[i]);
  return output;

console.log(formatString("Invalid {0} provided. A {1} must be provided for {0}.", "age", "number"));
// Invalid age provided. A number must be provided for age.

Try it yourself in this ES6 Fiddle.