Server-Side Rendering (SSR)

When using Element Plus for SSR development, you need to carry out special handling during SSR to avoid hydrate errors.

TIP

For Nuxt users, we provide a Nuxt module that contains these special processes. You only need to install it.

Provide an ID

The provided value is used to generate the unique ID in Element Plus. Because the different IDs are prone to hydrate errors in SSR, in order to ensure that the server side and client side generate the same ID, we need to inject the ID_injection_key into Vue.

// src/main.js (irrelevant code omitted)
import { createApp } from 'vue'
import { ID_INJECTION_KEY } from 'element-plus'
import App from './App.vue'

const app = createApp(App)
app.provide(ID_INJECTION_KEY, {
  prefix: 1024,
  current: 0,
})

Teleports

Teleport is used internally by multiple components in Element Plus (eg. ElDialog, ElDrawer, ElTooltip, ElDropdown, ElSelect, ElDatePicker ...), so special handling is required during SSR.

Render the Teleport on the mount

An easier solution is to conditionally render the Teleport on the mount.

For example, use the ClientOnly component in Nuxt.

<client-only>
  <el-tooltip content="the tooltip content">
    <el-button>tooltip</el-button>
  </el-tooltip>
</client-only>

or

<script setup>
import { ref } from 'vue'

const isClient = ref(false)

onMounted(() => {
  isClient.value = true
})
</script>

<template>
  <el-tooltip v-if="isClient" content="the tooltip content">
    <el-button>tooltip</el-button>
  </el-tooltip>
</template>

Inject the teleport markup

Another way is to inject the teleport markup into the correct location in your final page HTML.

WARNING

There may be some SSR problems with teleport, so you should pay attention to the following precautions.

  1. The teleported attribute in all components based on ElTooltip should be consistent, it is recommended to use the default value.
  2. The append-to-body attribute value of ElDialog and ElDrawer should be consistent, it is recommended to enable the append-to-body.
  3. When the ElSubMenu component has a multi-layer popup, It is recommended to enable the popper-append-to-body

You need to inject the teleport markup close to the <body> tag.

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Element Plus</title>
    <!--preload-links-->
  </head>
  <body>
    <!--app-teleports-->
    <div id="app"><!--app-html--></div>
    <script type="module" src="/src/entry-client.js"></script>
  </body>
</html>

TIP

If you modify the Namespace or append-to attribute, you need to adjust the #el-popper-container- value.

// src/entry-server.js (irrelevant code omitted)
import { renderToString } from 'vue/server-renderer'
import { createApp } from './main'

export async function render(url, manifest) {
  // ...
  const ctx = {}
  const html = await renderToString(app, ctx)
  const preloadLinks = renderPreloadLinks(ctx.modules, manifest)
  const teleports = renderTeleports(ctx.teleports)

  return [html, preloadLinks, teleports]
}

function renderTeleports(teleports) {
  if (!teleports) return ''
  return Object.entries(teleports).reduce((all, [key, value]) => {
    if (key.startsWith('#el-popper-container-')) {
      return `${all}<div id="${key.slice(1)}">${value}</div>`
    }
    return all
  }, teleports.body || '')
}

// server.js or prerender.js (irrelevant code omitted)
const [appHtml, preloadLinks, teleports] = await render(url, manifest)

const html = template
  .replace('<!--preload-links-->', preloadLinks)
  .replace('<!--app-html-->', appHtml)
  .replace(/(\n|\r\n)\s*<!--app-teleports-->/, teleports)