[JS] Function Bind

Why you need this?
 var x = 9;
var module = {
  x: 81,
  getX: function() { return this.x; }
};

module.getX(); // 81

var getX = module.getX;
getX(); // 9, because in this case, "this" refers to the global object

// create a new function with 'this' bound to module
var boundGetX = getX.bind(module);
boundGetX(); // 81

// ----------------------------------------------------

Function.prototype.bind = function(oThis) {
  var args = Array.prototype.slice.call(arguments, 1);
  var fToBind = this;
  var fToReturn = function() {
    return fToBind.apply(oThis, args.concat(Array.prototype.slice.call(arguments)))
  }
  return fToReturn;
}