初窥React-5(unbatchedUpdate方法)

function unbatchedUpdates(fn, a) {         //非常有趣的设计，类似锁、释放内存的设计
    var prevExecutionContext = executionContext; //0
    executionContext &= ~BatchedContext;         //1
    executionContext |= LegacyUnbatchedContext;  //8

    try {
      return fn(a); //执行updateContainer....
    } finally {
      executionContext = prevExecutionContext; //重置....

      if (executionContext === NoContext) {
        // Flush the immediate callbacks that were scheduled during this batch
        resetRenderTimer();
        flushSyncCallbackQueue();
      }
    }
  }