import { Callout } from 'nextra/components'

Data Fetching

const { data, error } = useSWR(key, fetcher)

This is the very fundamental API of SWR. The fetcher here is an async function that accepts the key of SWR, and returns the data.

The returned value will be passed as data, and if it throws, it will be caught as error.

<Callout> Note that `fetcher` can be omitted from the parameters if it's [provided globally](/docs/global-configuration). </Callout>

Fetch

You can use any library to handle data fetching, for example a fetch polyfill developit/unfetch:

import fetch from 'unfetch'

const fetcher = url => fetch(url).then(r => r.json())

function App() {
  const { data, error } = useSWR('/api/data', fetcher)
  // ...
}

<Callout> If you are using **Next.js**, you don't need to import this polyfill:

New Built-In Polyfills: fetch(), URL, and Object.assign

</Callout>

Axios

import axios from 'axios'

const fetcher = url => axios.get(url).then(res => res.data)

function App() {
  const { data, error } = useSWR('/api/data', fetcher)
  // ...
}

GraphQL

Or using GraphQL with libs like graphql-request:

import { request } from 'graphql-request'

const fetcher = query => request('/api/graphql', query)

function App() {
  const { data, error } = useSWR(
    /* GraphQL */ `
      {
        Movie(title: "Inception") {
          releaseDate
          actors {
            name
          }
        }
      }
    `,
    fetcher
  )
  // ...
}

If you want to pass variables to a GraphQL query, check out Multiple Arguments.