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data() hook

Environment: server (configurable).

The data() hook is used for fetching data. It's usually used together with useData().

See Guides > Data Fetching for an introduction about data() and fetching data in general.

For a lower-level hook with more control, see API > onBeforeRender() hook.

ORM/SQL

By default (it's configurable) the data() hook always runs the server-side, which means you can directly use ORM/SQL database queries:

// /pages/movies/+data.js
 
export { data }
 
// Note how we use `node-fetch`; this file is only run on the server-side, thus we don't need
// to use an isomorphic (aka universal) implementation such as `cross-fetch`.
import fetch from 'node-fetch'
 
async function data(pageContext) {
  const response = await fetch('https://star-wars.brillout.com/api/films.json')
  let { movies } = await response.json()
  /* Or with an ORM:
  let movies = await Movie.findAll() */
  /* Or with SQL:
  let movies = await sql.run('SELECT * FROM movies;') */
 
  // `movies` is serialized and passed to the client. Therefore, we pick only the
  // data the client needs in order to minimize what is sent over the network.
  movies = movies.map(({ title, release_date }) => ({ title, release_date }))
 
  return {
    movies
  }
}

Error handling

If an error is thrown by data(), then Vike renders your error page and there is usually nothing for you to do (beyond defining an error page /pages/_error/+Page.js).

But if you want a more precise error handling (such as showing an insightful error message to the user instead of some generic "Something went wrong"), then use throw render() and/or throw redirect().

// /pages/movies/+data.js
// Environment: server
 
export { data }
 
import fetch from 'node-fetch'
import { render, redirect } from 'vike/abort'
 
async function data(pageContext) {
  const { id } = pageContext.routeParams
  const response = await fetch(`https://star-wars.brillout.com/api/films/${id}.json`)
 
  if (response.status === 404) {
    // Tell the user what went wrong
    throw render(404, `Movie with ID ${id} doesn't exist.`)
    /* Or redirect the user:
    throw redirect('/movie/add') */
    /* Or render the movie submission form while preserving the URL:
    throw render('/movie/add') */
  }
 
  // ...
}

throw render('/movie/add') is a technique explained at Integration > Authentication > Login flow.

Alternatively, you can use throw render() and throw redirect() inside of a guard() hook, see Integration > Authentication.

Environment

By default, the data() hook always runs on the server-side.

By using .client.js (or .shared.js), you can tell Vike to only (or also) load and execute data() on the client-side.

Alternatively, instead of using .shared.js and .client.js, you can modify the meta.env setting of the data() hook in a global fashion, removing the need to add .shared.js / .client.js to each of your +data.js files.

Client-side only

By using .client.js, you can tell Vike to load and execute data() only on the client-side (never on the server-side).

For pre-rendered pages (SSG), if you want to fetch dynamic data provided by some server (Java/PHP/JavaScript/...), then make sure to always call data() on the client-side (i.e. +data.client.js).

Note that, for pre-rendered pages, the data that is fetched from the "server-side" is the static JSON file dist/client/some-page/index.pageContext.json that was generated at build-time upon pre-rendering the page.

Server- and client-side

By using .shared.js, you can tell Vike to load and execute data() also on the client-side:

  • data() runs on the server-side for the first page the user visits.
  • data() runs on the client-side for subsequent page navigations.

In general, we recommend running data() only on the server-side because it's easier to write code that runs in only one environment.

That said, if you want to minimize requests made to your server, then it can make sense to run data() also on the client-side. See:

Examples

React + JavaScript:

React + TypeScript:

Vue + JavaScript:

Vue + TypeScript:

TypeScript

See API > useData() > TypeScript.

Without vike-{react,vue,solid}

The data() hook is usually used together with the component hook useData() which is provided by the UI framework Vike extension vike-react/vike-vue/vike-solid.

In general, for improved DX, we recommend using data() together with a useData() implementation.

In case you don't use vike-react/vike-vue/vike-solid, you can implement useData() yourself as shown at API > useData() > Without vike-{react,vue,solid}

That said, you can also use data() without useData():

// /renderer/+onRenderHtml.js
// Environment: server
 
export { onRenderHtml }
 
import { escapeInject, dangerouslySkipEscape } from 'vike/server'
import { renderToHtml, createElement } from 'some-ui-framework'
 
async function onRenderHtml(pageContext) {
  // The data is available at pageContext.data
  const { Page, data } = pageContext
  const pageHtml = await renderToHtml(
    // Pass pageContext.data to the <Page> component
    createElement(Page, data)
  )
  /* JSX:
  const pageHtml = await renderToHtml(<Page {...data} />)
  */
 
  return escapeInject`<html>
    <div id='view-root'>
      ${dangerouslySkipEscape(pageHtml)}
    </div>
  </html>`
}
// /renderer/+onRenderClient.js
// Environment: browser
 
export { onRenderClient }
 
import { hydrateDom, createElement } from 'some-ui-framework'
 
async function onRenderClient(pageContext) {
  const { Page, data } = pageContext
  await hydrateDom(
    // Pass pageContext.data to the <Page> component
    createElement(Page, data),
    document.getElementById('view-root')
  )
  /* JSX:
  await hydrateDom(<Page {...data} />, document.getElementById('view-root'))
  */
}
// /pages/movies/+Page.js
// Environment: browser and server
 
export { Page }
 
// In the onRenderHtml() and onRenderClient() hooks above,
// pageContext.data is passed to the <Page> component.
function Page(data) {
  const { movies } = data
  // ...
}

See also