In JavaScript, binds an object to a callback function to use as "this".

bind_this.js

// In JavaScript, binds an object to a callback function to use as "this".
//
// When a function is passed as an event callback, "this" is bound to
// the DOM element triggering the event; in other scenarios when a
// function is used as a callback, "this" is bound to the window
// object.
//
// To override the default binding of "this", call bindThis on your
// function. For example:
//
//     camera.shootPhoto(
//         function (image) {
//             // ...
//         }.bindThis(someObject)
//     );
//              
Function.prototype.bindThis = function (context) {
    var self = this;
    return function () { self.apply(context, arguments); }
};