sebastian-software/core

/*
==================================================================================================
  Core - JavaScript Foundation
  Copyright 2010-2012 Zynga Inc.
  Copyright 2012-2014 Sebastian Werner
--------------------------------------------------------------------------------------------------
  Based on the work of Andrea Giammarchi
  Vice-Versa Project: http://code.google.com/p/vice-versa/
  http://webreflection.blogspot.com/2010/02/functionprototypebind.html
  MIT LICENSE
==================================================================================================
*/

"use strict";

/**
 * Adds missing ES5 `Function.prototype.bind` when not implemented natively by the browser engine.
 */
core.Main.addMembers("Function",
{
    /**
     * {Function} Binds the function to the specific @context {Object} with optionally bound arbitrary number of @varargs {var...?}.
     *
     * See also: https://developer.mozilla.org/en/JavaScript/Reference/Global_Objects/Function/bind
     */
    bind : function(context, varargs)
    {
        // closest thing possible to the ECMAScript 5 internal IsCallable function
        if (typeof this !== "function") {
            throw new TypeError();
        }

        // "trapped" function reference
        var self = this;
        var undef;

        // only if there is more than an argument
        // we are interested into more complex operations
        // this will speed up common bind creation
        // avoiding useless slices over arguments
        if (varargs !== undef)
        {
            // extra arguments to send by default
            var extraargs = Array.prototype.slice.call(arguments, 1);

            return function()
            {
                return self.apply(
                    context,
                    // thanks @kangax for this suggestion
                    arguments.length ?
                        // concat arguments with those received
                        extraargs.concat(Array.prototype.slice.call(arguments)) :
                        // send just arguments, no concat, no slice
                        extraargs
                );
            };
        }
        else
        {
            // optimized callback
            return function()
            {
                // speed up when function is called without arguments
                return arguments.length ? self.apply(context, arguments) : self.call(context);
            };
        }
    }
});