process.nextTick(callback[, ...args])

• callback <Function>

• ...args <any> 当调用 callback 时要传入的额外参数

  ¥...args <any> Additional arguments to pass when invoking the callback

process.nextTick() 将 callback 添加到 "下一个滴答队列"。在 JavaScript 堆栈上的当前操作运行完成之后，且在允许事件循环继续之前，此队列将被完全排空。如果递归地调用 process.nextTick()，则可能会创建无限的循环。有关更多背景信息，请参阅 事件循环 指南。

¥process.nextTick() adds callback to the "next tick queue". This queue is fully drained after the current operation on the JavaScript stack runs to completion and before the event loop is allowed to continue. It's possible to create an infinite loop if one were to recursively call process.nextTick(). See the Event Loop guide for more background.

import { nextTick } from 'node:process';

console.log('start');
nextTick(() => {
  console.log('nextTick callback');
});
console.log('scheduled');
// Output:
// start
// scheduled
// nextTick callbackconst { nextTick } = require('node:process');

console.log('start');
nextTick(() => {
  console.log('nextTick callback');
});
console.log('scheduled');
// Output:
// start
// scheduled
// nextTick callback拷贝

这在开发 API 时很重要，以便让用户有机会在对象构建之后但在任何 I/O 发生之前分配事件处理程序：

¥This is important when developing APIs in order to give users the opportunity to assign event handlers after an object has been constructed but before any I/O has occurred:

import { nextTick } from 'node:process';

function MyThing(options) {
  this.setupOptions(options);

  nextTick(() => {
    this.startDoingStuff();
  });
}

const thing = new MyThing();
thing.getReadyForStuff();

// thing.startDoingStuff() gets called now, not before.const { nextTick } = require('node:process');

function MyThing(options) {
  this.setupOptions(options);

  nextTick(() => {
    this.startDoingStuff();
  });
}

const thing = new MyThing();
thing.getReadyForStuff();

// thing.startDoingStuff() gets called now, not before.拷贝

这对于要 100% 同步或 100% 异步的 API 非常重要。设想这个示例：

¥It is very important for APIs to be either 100% synchronous or 100% asynchronous. Consider this example:

// WARNING!  DO NOT USE!  BAD UNSAFE HAZARD!
function maybeSync(arg, cb) {
  if (arg) {
    cb();
    return;
  }

  fs.stat('file', cb);
} 拷贝

此 API 是危险的，因为在以下情况下：

¥This API is hazardous because in the following case:

const maybeTrue = Math.random() > 0.5;

maybeSync(maybeTrue, () => {
  foo();
});

bar(); 拷贝

并不清楚是先调用 foo() 还是 bar()。

¥It is not clear whether foo() or bar() will be called first.

以下方法要好得多：

¥The following approach is much better:

import { nextTick } from 'node:process';

function definitelyAsync(arg, cb) {
  if (arg) {
    nextTick(cb);
    return;
  }

  fs.stat('file', cb);
}const { nextTick } = require('node:process');

function definitelyAsync(arg, cb) {
  if (arg) {
    nextTick(cb);
    return;
  }

  fs.stat('file', cb);
}拷贝