queueMicrotask(callback)

• callback <Function> 要排队的函数。

  \callback <Function> Function to be queued.

queueMicrotask() 方法将微任务排队以调用 callback。如果 callback 抛出异常,将触发 process 对象 'uncaughtException' 事件。

\The queueMicrotask() method queues a microtask to invoke callback. If callback throws an exception, the process object 'uncaughtException' event will be emitted.

微任务队列由 V8 管理,并且可以以类似于 process.nextTick() 队列的方式使用,后者由 Node.js 管理。在 Node.js 事件循环的每次轮询中,process.nextTick() 队列总是在微任务队列之前处理。

\The microtask queue is managed by V8 and may be used in a similar manner to the process.nextTick() queue, which is managed by Node.js. The process.nextTick() queue is always processed before the microtask queue within each turn of the Node.js event loop.

// Here, `queueMicrotask()` is used to ensure the 'load' event is always
// emitted asynchronously, and therefore consistently. Using
// `process.nextTick()` here would result in the 'load' event always emitting
// before any other promise jobs.
DataHandler.prototype.load = async function load(key) {
 const hit = this._cache.get(key);
 if (hit !== undefined) {
 queueMicrotask(() => {
 this.emit('load', hit);
 });
 return;
 }
 const data = await fetchData(key);
 this._cache.set(key, data);
 this.emit('load', data);
}; 拷贝