effector

The state manager

Explainer video

import {createEvent, createStore, createEffect, sample} from 'effector'

const nextPost = createEvent()

const getCommentsFx = createEffect(async postId => {
  const url = `posts/${postId}/comments`
  const base = 'https://jsonplaceholder.typicode.com'
  const req = await fetch(`${base}/${url}`)
  return req.json()
})

const $postComments = createStore([])
  .on(getCommentsFx.doneData, (_, posts) => posts)

const $currentPost = createStore(1)
  .on(getCommentsFx.done, (_, {params: postId}) => postId)

const $status = combine(
  $currentPost, $postComments, getCommentsFx.pending,
  (postId, comments, isLoading) => isLoading
    ? 'Loading post...'
    : `Post ${postId} has ${comments.length} comments`
)

sample({
  source: $currentPost,
  clock: nextPost,
  fn: postId => postId + 1,
  target: getCommentsFx,
})

$status.watch(status => {
  console.log(status)
})
// => Post 1 has 0 comments

nextPost()

// => Loading post... 
// => Post 2 has 5 comments 

Type safe

TypeScript and Flow support out of box.

Framework agnostic

Can work with any UI or server framework.

Developer-friendly

Simple API surface and helpful community.

Maximum performance

Static initialization provides boost in performance for runtime.

Tiny bundle size

Effector uses Rollup and Terser to provide small builds.

Plain javascript

No decorators, no proxies, no classes required. Only you and your data.