code: function(object, data, handler, acceptList) {
              var hdata = handlers.get(handler), odata;
              if (!hdata)
                  handlers.set(handler, hdata = {
                      observed: createMap(),
                      changeRecords: []
                  });
              hdata.observed.set(object, {
                  acceptList: acceptList.slice(),
                  data: data
              });
              data.handlers.set(handler, hdata);
          }
docs: Functions for internal usage 
  Checks if the argument is an Array object. Polyfills Array.isArray.
  @function isArray
  @param {?*} object
  @returns {Boolean}