Function.prototype.bind performance problem solved in JS … (at least for 90% of common cases without partial args)

fast-bind.js

/*jslint indent: 2 */
(function (FunctionPrototype) {
  'use strict';
  var originalBind = FunctionPrototype.bind;
  if (!originalBind.patched) {
    Object.defineProperty(
      FunctionPrototype,
      'bind',
      {
        configurable: true,
        value: function bind(context) {
          var callback = this;
          return arguments.length === 1 ?
              function () { return callback.apply(context, arguments); } :
              originalBind.apply(callback, arguments);
        }
      }
    );
    FunctionPrototype.bind.patched = true;
  }
}(Function.prototype));

function foo() {
   console.log(this.x);
}

var context = { x: 123 };
var boundFunction = foo.bind(context);

boundFunction();     // prints 123
new boundFunction(); // prints undefined

The edge case is the last statement. When boundFunction is called through the new operator, the receiver (this) is set to the object being created by new, not the original context object.

I'm not sure, but this behavior may've been designed to allow constructor functions to take advantage of bind's partial application without the undesired side effect of setting this. For example:

function Car(make, model, year) {
  this.make = make;
  this.model = model;
  this.year = year;
}

var festivaFactory = Car.bind(null /*doesn't matter*/, "Ford", "Festiva");
var oldCar = new festivaFactory(1989);    // {make: "Ford", model: "Festiva", year: 1989}
var newerCar = new festivaFactory(1993);  // {make: "Ford", model: "Festiva", year: 1993}

The code above would not work as intended if the bound function received this == null when invoked through new. Of course, there are other ways of achieving the same effect.