Web API setImmediate & Node.js setImmediate All In One

Web API setImmediate & Node.js setImmediate All In One

Window.setImmediate()

setImmediate 没有 delay 参数 ⚠️

setImmediate(func)

setImmediate(func, param0)
setImmediate(func, param0, param1)
setImmediate(func, param0, param1, /* … ,*/ paramN)

https://developer.mozilla.org/en-US/docs/Web/API/Window/setImmediate

setTimeout

setTimeout 有 delay 参数 ✅

setTimeout(func)

setTimeout(func, delay)
setTimeout(func, delay, param1)
setTimeout(func, delay, param1, param2)
setTimeout(func, delay, param1, param2, /* … ,*/ paramN)

// code ⚠️
setTimeout(code)
setTimeout(code, delay)

https://developer.mozilla.org/en-US/docs/Web/API/setTimeout

setInterval

setInterval 有 delay 参数 ✅

setTimeout(func)

setTimeout(func, delay)
setTimeout(func, delay, param1)
setTimeout(func, delay, param1, param2)
setTimeout(func, delay, param1, param2, /* … ,*/ paramN)

// code ⚠️
setInterval(code)
setInterval(code, delay)

https://developer.mozilla.org/en-US/docs/Web/API/setInterval

Web API setImmediate support warning ⚠️

https://caniuse.com/?search=setImmediate

Note: This method is not expected to become standard, and is nowadays only implemented by Node.js 0.10+.
It meets resistance both from Gecko (Firefox) and Chromium/WebKit (Chrome/Safari).

https://bugzilla.mozilla.org/show_bug.cgi?id=686201

https://bugs.chromium.org/p/chromium/issues/detail?id=146172

Window.setImmediate() error ❌

Uncaught ReferenceError: setImmediate is not defined

// alert() 后进行 console.log，如果没有关闭弹框，控制台是不会显示出一条 log
// 阻塞进程
alert(`delay`);

const log = console.log;

let id = setInterval(() => {
  log(`4`);
  clearInterval(id);
}, 0);

setTimeout(() => {
  log(`3`);
}, 0);

log(`1`);

setImmediate(() => {
  log(`2`);
}, 0);


/*
1
// ❌ Uncaught ReferenceError: setImmediate is not defined
3
4
*/

Node.js setImmediate ✅

如果在 Node.js 主进程中直接执行这两个操作(setInterval 与 setTimeout)，无法保证哪个会先触发。⚠️

1. 如果 setInterval 与 setTimeout 的 delay 为 0，那个在前保证哪个会先触发；但是 setImmediat 貌似最慢 ❓why

const log = console.log;

setImmediate(() => {
  log(`5`);
});

let n = 0;
let id = setInterval(() => {
  log(`4`);
  clearInterval(id);
}, 0);

setTimeout(() => {
  log(`3`);
}, 0);

process.nextTick(() => {
  log(`2`);
});

log(`1`);

/*
$ node ./setImmediate.js

1
2
4
3
5
*/

const log = console.log;

setImmediate(() => {
  log(`5`);
});

setTimeout(() => {
  log(`4`);
}, 0);

let n = 0;
let id = setInterval(() => {
  log(`3`);
  clearInterval(id);
}, 0);

process.nextTick(() => {
  log(`2`);
});

log(`1`);

/*
$ node ./setImmediate.js

1
2
4
3
5
*/

2. 如果 setInterval 与 setTimeout 的 delay 不为 0， setImmediat 会最先于 setInterval 与 setTimeout 执行，毕竟没有 delay.

const log = console.log;

let n = 0;
let id = setInterval(() => {
  log(`4`);
  clearInterval(id);
}, 1000);

/* let n = 0;
let id = setInterval(() => {
  log(`4`, n);
  if(n < 10) {
    n++;
  } else {
    n = 0;
    clearInterval(id);
  }
}, 0); */

setTimeout(() => {
  log(`5`);
}, 1000);

setImmediate(() => {
  log(`3`);
});

process.nextTick(() => {
  log(`2`);
});

log(`1`);

/*

1
2
3

4
5

*/

process.nextTick vs setImmediate

const baz = () => console.log('baz');
const foo = () => console.log('foo');
const zoo = () => console.log('zoo');

const start = () => {
  console.log('start');
  setImmediate(baz);
  new Promise((resolve, reject) => {
    resolve('bar');
  }).then((resolve) => {
    console.log(resolve);
    process.nextTick(zoo);
  });
  process.nextTick(foo);
};

start();

// start foo bar zoo baz

https://nodejs.dev/en/learn/understanding-setimmediate/

import { nextTick } from 'node:process';

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

https://nodejs.org/api/process.html#processnexttickcallback-args

queueMicrotask() vs. process.nextTick()

import { nextTick } from 'node:process';

Promise.resolve().then(() => console.log(2));
queueMicrotask(() => console.log(3));
nextTick(() => console.log(1));
// Output:
// 1
// 2
// 3

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

https://nodejs.org/api/process.html#when-to-use-queuemicrotask-vs-processnexttick

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refs

process.nextTick

https://medium.com/@amanhimself/how-process-nexttick-works-in-node-js-cb327812e083

https://timnew.me/blog/2014/06/23/process-nexttick-implementation-in-browser/

https://www.geeksforgeeks.org/difference-between-process-nexttick-and-setimmediate-methods/

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