code: function setState(state, callback) {
        var s = this.state;
        if (!this.prevState) this.prevState = extend({}, s);
        extend(s, typeof state === 'function' ? state(s, this.props) : state);
        if (callback) (this._renderCallbacks = this._renderCallbacks || []).push(callback);
        enqueueRender(this);
      }
docs: Returns a `boolean` indicating if the component should re-render when receiving the given `props` and `state`.
  @param {object} nextProps
  @param {object} nextState
  @param {object} nextContext
  @return {Boolean} should the component re-render
  @name shouldComponentUpdate
  @function
   Update component state by copying properties from `state` to `this.state`.
  @param {object} state		A hash of state properties to update with new values
  @param {function} callback	A function to be called once component state is updated