suspend-react

npm install suspend-react

This library integrates your async ops into React suspense. Error-handling & loading states are handled at the parental level. The individual component functions similar to async/await in Javascript.

• Chain your operations synchronously
• No useEffect/setState hassle
• No checking for the presence of your data
• All React versions >= 16.6

import { Suspense } from 'react'
import { suspend } from 'suspend-react'

function Post({ id, version }) {
  const data = suspend(async (/*id, version*/) => {
    const res = await fetch(`https://hacker-news.firebaseio.com/${version}/item/${id}.json`)
    return await res.json()
  }, [id, version])
  return <div>{data.title} by {data.by}</div>
}

function App() {
  return (
    <Suspense fallback={<div>loading...</div>}>
      <Post id={1000} version="v0" />
    </Suspense>
  )
}

API

const result = suspend((...keys) => Promise<any>, keys: any[], config)

When you call suspend it yields control back to React and the render-phase is aborted. It will resume once your promise resolves. For this to work you need to wrap it into a <React.Suspense> boundary, which requires you to set a fallback (which can be null).

The dependencies/keys act as cache-keys, use as many as you want. If an entry is already in cache, calling suspend with the same keys will return it immediately, without breaking the render-phasse. Cache access is similar to useMemo but across the component tree. The first-arg function has to return a thenable (async function or a promise), it receives the keys as arguments. suspend will return the resolved value, not a promise! This is guaranteed, you do not have to check for validity. Errors will bubble up to the nearest error-boundary.

Config

Both suspend and preload can optionally reveive a config object,

Keep-alive

The lifespan prop allows you to invalidate items over time, it defaults to 0 (keep-alive forever).

// Keep cached item alive for one minute
suspend(fn, keys, { lifespan: 60000 })

Equality function

The equal prop customizes key validation, it defaults to (a, b) => a === b (reference equality).

import equal from 'fast-deep-equal'

// Validate keys deeply
suspend(fn, keys, { equal })

Preloading

import { preload } from 'suspend-react'

async function fetchFromHN(id, version) {
  const res = await fetch(`https://hacker-news.firebaseio.com/${version}/item/${id}.json`)
  return await res.json()
}

preload(fetchFromHN, [1000, 'v0'])

Cache busting

import { clear } from 'suspend-react'

// Clear all cached entries
clear()
// Clear a specific entry
clear([1000, 'v0'])

Peeking into entries outside of suspense

import { peek } from 'suspend-react'

// This will either return the value (without suspense!) or undefined
peek([1000, 'v0'])

Typescript

Correct types will be inferred automatically.

React 18

Suspense, as is, has been a stable part of React since 16.6, but React will likely add some interesting caching and cache busting APIs that could allow you to define cache boundaries declaratively. Expect these to be work for suspend-react once they come out.

Demos

Fetching posts from hacker-news: codesandbox

Infinite list: codesandbox