forEach-wrong.js

if (!Array.prototype.forEach) {
  Array.prototype.forEach = function(callback, thisArg) {
    if (this === null) {
      throw new TypeError('Array.prototype.forEach called on null or undefined');
    }
    if (typeof callback !== "function") {
      throw new TypeError(callback + ' is not a function');
    }
    var len = this.length || 0;
    for(var i=0; i<len;i++){
    	callback.call(thisArg, this[i], i, this);
    }
  };
}