streamich / entask

Micro- and Macro-tasks for Node and browsers

entask

Enqueue micro-tasks and macro-tasks in browser and Node.js. Only 0.3Kb in weight and 60 lines of code in length.

What are micro- vs macro-tasks?

In Node.js and browsers macro-tasks are functions scheduled to be executed in future event loop cycles, for example setTimeout(fn, 0) will schedule fn to be executed in one of the future event loop cycles.

On the other hand, all callbacks in micro-task queue will execute before the current event loop cycle finishes, for example in Node.js callbacks scheduled using process.nextTick(fn) will all execute in the current event loop cycle.

Install

npm install entask

Usage

import {microtask, macrotask, asap} from 'entask';

macrotask(() => console.log('world!'));
microtask(() => console.log('Hello'));
// 👉 Hello world!

or

macrotask(() => console.log('C'));
microtask(() => console.log('B'));
console.log('A');
// 👉 A
// 👉 B
// 👉 C

Reference

microtask

Will schedule a micro-task, it will try to use the following methods in this order:

1. process.nextTick
2. Promise
3. MutationObserver
4. WebkitMutationObserver

If none of the methods are available, microtask itself will equal to null.

macrotask

Will schedue a macro-task, it will try to use the following methods in this order:

1. setImmediate
2. MessageChannel
3. window.postMessage
4. setTimeout

If you are running in Node.js or browser environemnt, then macrotask will at least default to setTimeout. If you are running in an evironment that does not even have setTimeout method, macrotask may equal to null.

asap

It is defined as

const asap = microtask || macrotask;

i.e. asap will try to schedule a micro-task but fall back to scheduling a macro-task.

Lite

You can also use light version.

import {microtask, macrotask, asap} from 'entask/lite';

It has the same API but does not include MutationObserver, because almost all modern browsers will have Promise implementation. It also does not include window.postMessage, because almost all modern browsers have MessageChannel implementation available.

Shims

You can shim process.nextTick in your browser.

require('entask/shim/nexttick').install();
process.nextTick(() => { /* ... */ });

You can also shim setImmediate.

require('entask/shim/setimmediate').install();
setImmediate(() => { /* ... */ });

License

Unlicense — public domain.

entask's Issues

MessageChannel didn't close

entask/index.js

Lines 32 to 34 in 23a1b5c

	var channel = new MessageChannel();
	channel.port1.onmessage = function () { fn(); };
	channel.port2.postMessage(0);

The MessageChannel instance won't close if you don't call channel.port1.close() after fn() is executed.