next.js/test/development/pages-dir/client-navigation/fixture/pages/head.js

import React from 'react'
import Head from 'next/head'

export default function HeadPage() {
  const [shouldReverseScriptOrder, reverseScriptOrder] = React.useReducer(
    (b) => !b,
    false
  )
  const [shouldInsertScript, toggleScript] = React.useReducer((b) => !b, false)

  const scriptAsyncTrue = <script src="/test-async-true.js" async></script>
  const scriptAsyncFalse = (
    <script src="/test-async-false.js" async={false}></script>
  )

  return (
    <div>
      <Head>
        {/* this will not render */}
        <meta charSet="utf-8" />
        {/* this will get rendered */}
        <meta charSet="iso-8859-5" />

        {/* this will not render */}
        <meta name="viewport" content="width=device-width" />
        {/* this will override the default */}
        <meta name="viewport" content="width=device-width,initial-scale=1" />

        <meta content="my meta" />

        {/* this will not render the content prop */}
        <meta name="empty-content" content={undefined} />

        {/* allow duplicates for specific tags */}
        <meta property="article:tag" content="tag1" key="tag1key" />
        <meta property="article:tag" content="tag2" key="tag2key" />
        <meta property="dedupe:tag" content="tag3" key="same-key" />
        <meta property="dedupe:tag" content="tag4" key="same-key" />
        <meta property="og:image" content="ogImageTag1" key="ogImageTag1Key" />
        <meta property="og:image" content="ogImageTag2" key="ogImageTag2Key" />
        <meta
          property="og:image:alt"
          content="ogImageAltTag1"
          key="ogImageAltTag1Key"
        />
        <meta
          property="og:image:alt"
          content="ogImageAltTag2"
          key="ogImageAltTag2Key"
        />
        <meta
          property="og:image:width"
          content="ogImageWidthTag1"
          key="ogImageWidthTag1Key"
        />
        <meta
          property="og:image:width"
          content="ogImageWidthTag2"
          key="ogImageWidthTag2Key"
        />
        <meta
          property="og:image:height"
          content="ogImageHeightTag1"
          key="ogImageHeightTag1Key"
        />
        <meta
          property="og:image:height"
          content="ogImageHeightTag2"
          key="ogImageHeightTag2Key"
        />
        <meta
          property="og:image:type"
          content="ogImageTypeTag1"
          key="ogImageTypeTag1Key"
        />
        <meta
          property="og:image:type"
          content="ogImageTypeTag2"
          key="ogImageTypeTag2Key"
        />
        <meta
          property="og:image:secure_url"
          content="ogImageSecureUrlTag1"
          key="ogImageSecureUrlTag1Key"
        />
        <meta
          property="og:image:secure_url"
          content="ogImageSecureUrlTag2"
          key="ogImageSecureUrlTag2Key"
        />
        <meta
          property="og:image:url"
          content="ogImageUrlTag1"
          key="ogImageUrlTag1Key"
        />
        <meta
          property="og:image:url"
          content="ogImageUrlTag2"
          key="ogImageUrlTag2Key"
        />

        <meta property="fb:pages" content="fbpages1" />
        <meta property="fb:pages" content="fbpages2" />

        {/* both meta tags will be rendered since they use unique keys */}
        <meta
          name="citation_author"
          content="authorName1"
          key="citationAuthorTag1"
        />
        <meta
          name="citation_author"
          content="authorName2"
          key="citationAuthorTag2"
        />

        <React.Fragment>
          <title>Fragment title</title>
          <meta content="meta fragment" />
        </React.Fragment>

        {/* the following 2 link tags will both be rendered */}
        <link rel="stylesheet" href="/dup-style.css" />
        <link rel="stylesheet" href="/dup-style.css" />

        {/* only one tag will be rendered as they have the same key */}
        <link rel="stylesheet" href="dedupe-style.css" key="my-style" />
        <link rel="stylesheet" href="dedupe-style.css" key="my-style" />

        {shouldInsertScript ? scriptAsyncTrue : null}
        {/* this should not execute twice on the client */}
        {shouldReverseScriptOrder ? scriptAsyncTrue : scriptAsyncFalse}
        {/* this should have async set to false on the client */}
        {shouldReverseScriptOrder ? scriptAsyncFalse : scriptAsyncTrue}
        {/* this should not execute twice on the client (intentionally sets defer to `yas` to test boolean coercion) */}
        <script src="/test-defer.js" defer="yas"></script>

        {/* such style can be used for alternate links on _app vs individual pages */}
        {['pl', 'en'].map((language) => (
          <link
            rel="alternate"
            key={language}
            hrefLang={language}
            href={'/first/' + language}
          />
        ))}
        {['pl', 'en'].map((language) => (
          <link
            rel="alternate"
            key={language}
            hrefLang={language}
            href={'/last/' + language}
          />
        ))}
      </Head>
      <h1>I can have meta tags</h1>
      <button id="reverseScriptOrder" onClick={reverseScriptOrder}>
        Reverse script order
      </button>
      <button id="toggleScript" onClick={toggleScript}>
        Toggle script
      </button>
    </div>
  )
}