//indexOf实现
// http://webreflection.blogspot.fr/2011/06/partial-polyfills.html
function indexOf(value) {
  for (var i = this.length; i-- && this[i] !== value;) {}
  return i;
}
var arr = [0, 1, 2, 3, 4];
indexOf.call(arr, 4);

// each的实现
function each(ary, func) {
    if (ary) {
        var i;
        for (i = 0; i < ary.length; i += 1) {
            if (ary[i] && func(ary[i], i, ary)) {
                break;
            }
        }
    }
}
var arr = [1,2,3,4]
each(arr, function(value, index) {console.log(value)})