code: function Object_keys(obj) { // @arg Object|Function|Array
                              // @ret KeyStringArray [key, ... ]
      var result = [], key, i = 0;
  
      // [IE6][IE7][IE8] host-objects has not hasOwnProperty
      if ( !("hasOwnProperty" in obj) ) {
          for (key in obj) {
              result[i++] = key;
          }
      } else {
          for (key in obj) {
              if ( obj["hasOwnProperty"](key) ) {
                  result[i++] = key;
              }
          }
      }
      return result;
  }
docs: {@es5 === Object ==============================================