javascript Array.prototype.map implement.

Array.prototype.map.js

!function(){
  if( typeof Array.prototype.map == 'function')
  return;

  Array.prototype.map = function(callback){
    var i = 0,
      length = this.length,
      res = [];
    if( callback && typeof callback == 'function' ){
      for(;i<length;i++)
        res[i] = callback(this[i]);
    }
    return res;
  }
}();