IE8以前で forEach が使えるようにする

main.js

/** 
 * forEachをサポートしていないIE8以前で forEach が使えるようにする
 *
 * Production steps of ECMA-262, Edition 5, 15.4.4.18
 * Reference: http://es5.github.com/#x15.4.4.18
 * https://developer.mozilla.org/ja/docs/JavaScript/Reference/Global_Objects/Array/forEach
 * https://gist.github.com/oreo3/76595108a85ae4d6883a
 */
if (!Array.prototype.forEach) {
  Array.prototype.forEach = function(callback, thisArg) {
    var T, k;
    if (this === null) {
      throw new TypeError("this is null or not defined");
    }
    var O = Object(this);
    var len = O.length >>> 0;
    if ({}.toString.call(callback) != "[object Function]") {
      throw new TypeError(callback + " is not a function");
    }
    if (thisArg) {T = thisArg;}
    k = 0;
    while(k < len) {
      var kValue;
      if (k in O) {
        kValue = O[k];
        callback.call(T, kValue, k, O);
      }
      k++;
    }
  };
}