npm package discovery and stats viewer.

Discover Tips

  • General search

    [free text search, go nuts!]

  • Package details

    pkg:[package-name]

  • User packages

    @[username]

Sponsor

Optimize Toolset

I’ve always been into building performant and accessible sites, but lately I’ve been taking it extremely seriously. So much so that I’ve been building a tool to help me optimize and monitor the sites that I build to make sure that I’m making an attempt to offer the best experience to those who visit them. If you’re into performant, accessible and SEO friendly sites, you might like it too! You can check it out at Optimize Toolset.

About

Hi, 👋, I’m Ryan Hefner  and I built this site for me, and you! The goal of this site was to provide an easy way for me to check the stats on my npm packages, both for prioritizing issues and updates, and to give me a little kick in the pants to keep up on stuff.

As I was building it, I realized that I was actually using the tool to build the tool, and figured I might as well put this out there and hopefully others will find it to be a fast and useful way to search and browse npm packages as I have.

If you’re interested in other things I’m working on, follow me on Twitter or check out the open source projects I’ve been publishing on GitHub.

I am also working on a Twitter bot for this site to tweet the most popular, newest, random packages from npm. Please follow that account now and it will start sending out packages soon–ish.

Open Software & Tools

This site wouldn’t be possible without the immense generosity and tireless efforts from the people who make contributions to the world and share their work via open source initiatives. Thank you 🙏

© 2024 – Pkg Stats / Ryan Hefner

mobx-autorun-cleanup

v1.3.0

Published

Mobx autorun function with cleanup callback

Downloads

12

Readme

mobx-autorun-cleanup

Mobx autorun function with cleanup callback

Created with TS-Standard - Typescript Standard Style Guide

Inspired By

This is very similar to the React useEffect hook.

Example

import autorunCleanup from 'mobx-autorun-cleanup'
import { observable } from 'mobx'

const obj = observable({ theme: 'light' })

const stop = autorunCleanup(() => {
  const currentTheme = obj.theme
  console.log('Load', currentTheme)
  return () => {
    console.log('Unload', currentTheme)
  }
})
// Logs: Load light

obj.theme = 'dark'
// Logs:
// Unload light
// Load dark

// If you want
stop()
// Logs: Unload dark

Differences with mobx built-in reaction

mobx-autorun-cleanup is actually very similar to reaction, which is part of mobx.

Feature | reaction | mobx-autorun-cleanup --- | --- | --- Fn gets called first time | ❌ | ✔️ Fn is called after reactions | ✔️ | ✔️ Cleanup after reactions | ✔️ | ✔️ Cleanup after stopped | ❌ | ✔️ Cleanup is optional | ✔️ | ✔️ Separated code for reactions and side effects | ✔️ | ❌

Here is the same example, but it uses reaction instead of mobx-autorun-cleanup:

import { observable, reaction } from 'mobx'

const obj = observable({ theme: 'light' })

console.log('Load', obj.theme)
// Logs: Load light

const stop = reaction(() => obj.theme, (currentTheme, previousTheme) => {
  console.log('Unload', previousTheme)
  console.log('Load', currentTheme)
})
// Nothing is called until `obj.theme` is changed

obj.theme = 'dark'
// Logs:
// Unload light
// Load dark

// If you want
stop()
// Nothing is logged, because there is no cleanup fn
// You can now specify to unload
console.log('Unload', obj.theme)
// Logs: Unload dark

How to choose between the two

One way to think about the lifetime of the function and cleanup function is like a sandwich:

  • The first bread is when the function gets initially called
  • The stuff inside is when the function gets re-run after a reaction
  • The last bread is when the reaction is stopped

reaction only calls the function in the middle of the sandwich. mobx-autorun-cleanup additionally calls the function initially, and calls the cleanup function in the end.

Based on this comparison, you can decide which function to use. I think generally reaction is for side effects, and mobx-autorun-cleanup is for cleanup.

Typedoc

https://chocolateloverraj.github.io/mobx-autorun-cleanup