SWR — React Hooks library for data fetching

From the Next.js folks comes SWR, a React Hooks library for data fetching built on Suspense:

The name “SWR” is derived from stale-while-revalidate, a cache invalidation strategy popularized by HTTP RFC 5861. SWR first returns the data from cache (stale), then sends the fetch request (revalidate), and finally comes with the up-to-date data again.

It can avoid scenarios where you need to pass down a fetched user into several child components

import useSWR from 'swr'

const fetcher = (...args) => fetch(...args).then(res => res.json())

function useUser (id) {
  const { data, error } = useSWR(`/api/user/${id}`, fetcher)

  return {
    user: data,
    isLoading: !error && !data,
    isError: error
  }
}

// page component
function Page () {
  return <div>
    <Navbar />
    <Content />
  </div>
}

// child components
function Navbar () {
  return <div>
    ...
    <Avatar />
  </div>
}

function Content () {
  const { user, isLoading } = useUser()
  if (isLoading) return <Spinner />
  return <h1>Welcome back, {user.name}</h1>
}

function Avatar () {
  const { user, isLoading } = useUser()
  if (isLoading) return <Spinner />
  return <img src={user.avatar} alt={user.name} />
}

With SWR being used, this will result in only 1 request to /api/user/${id}.

The most beautiful thing is that there will be only 1 request sent to the API, because they use the same SWR key and the request is deduped, cached and shared automatically.

SWR — React Hooks library for data fetching →