Code Syntax highlighting in Next Js

If you're running blog page or website you know that adding syntax highlighting can be very tough and complex process. but fortunately I have found a way to add syntax highlighting in your next js blog website.

To add syntax highlighting in next js website we are gonna use library called highlightjs. This library supports ton of languages and themes for customizing as per your needs.

Let's get started by installing the highlight js

Setup

we can use yarn or npm to install this package.



npm install highlight.js
# or
yarn add highlight.js

After installation we import this package in our file. For me I'm gonna be using [slug].js which is basically dynamic page for blog posts.



import hljs from "highlight.js/lib/core";

Now we will need to import some of the required files for this package using <script/> tag but since we're using next js we're gonna use next/script.



import Script from "next/script";

Now to use this feature we have to enable experimental feature in our next config file.

next.config.js



module.exports = {
  experimental: {
    nextScriptWorkers: true,
  },
};

We're done with config file. Now we head back to our [slug].js file and start using <Script/> tag



import Script from "next/script";

const post = ({ post }) => {
  return (
    <>
      <div>{/*Post content goes here*/}</div>
    </>
  );
};

This is our basic setup now let's import highlight.js file using our <Script/> tag

Importing highlight.js



import Script from "next/script";

const post = ({ post }) => {
  return (
    <>
      <Script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></Script>
      {/* Import highlight js */}
      <div>{/* Post content goes here */}</div>
    </>
  );
};

Importing stylesheet for highlighting

Now after importing highlight.js library we'll need to import stylesheet for highlighting. In our next js project we have a file _document.js we'll import this stylesheet in that page.



import { Html, Head, Main, NextScript } from "next/document";

export default function Document() {
  return (
    <Html lang="en">
      <Head />
      <body>
        <Main />
        <NextScript />
      </body>
    </Html>
  );
}

This is my _document.js, yours can be different depends on the project. We import the stylesheet inside the Head tag which is basically replacement of default <head/> to <Head/> by next js.



import { Html, Head, Main, NextScript } from "next/document";

export default function Document() {
  return (
    <Html lang="en">
      <Head>
        <link
          rel="stylesheet"
          href="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/styles/tokyo-night-dark.min.css"
        />
      </Head>
      <body>
        <Main />
        <NextScript />
      </body>
    </Html>
  );
}

Here I have imported the stylesheet inside the Head tag. You can find large collection of these stylesheet here. Just select the Asset type to Styling and keep experimenting with theme until you find the right one.

We're done with the _document.js file. let's head back to [slug].js and finish the final process.

Now to enable syntax highlighting for various languages we need to register those languages.

[slug].js



import Script from "next/script";

const post = ({ post }) => {
  return (
    <>
      <Script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></Script>
      {/* Import highlight js */}
      <div>{/* Post content goes here */}</div>
    </>
  );
};

First let's import the highlight.js.



import Script from "next/script";
import hljs from "highlight.js/lib/core";

const post = ({ post }) => {
  return (
    <>
      <Script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></Script>
      {/* Import highlight js */}
      <div>{/* Post content goes here */}</div>
    </>
  );
};

Enabling various language support

Now let's import various languages highlighting support



import Script from "next/script";

// Importing libraries
import hljs from "highlight.js/lib/core";

// Importing languages
import sql from "highlight.js/lib/languages/sql";
import javascript from "highlight.js/lib/languages/javascript";
import c from "highlight.js/lib/languages/c";
import css from "highlight.js/lib/languages/css";
import scss from "highlight.js/lib/languages/scss";
import shell from "highlight.js/lib/languages/shell";
import python from "highlight.js/lib/languages/python";
import powershell from "highlight.js/lib/languages/powershell";
import cpp from "highlight.js/lib/languages/cpp";
import php from "highlight.js/lib/languages/php";
import phpTemplate from "highlight.js/lib/languages/php-template";
import xml from "highlight.js/lib/languages/xml";

const post = ({ post }) => {
  return (
    <>
      <Script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></Script>
      {/* Import highlight js */}
      <div>{/* Post content goes here */}</div>
    </>
  );
};

Here I have import most common languages but you can find more languages in the list.

Registering languages for highlighting

Now we register these languages. We'll need to useEffect() to register these language onReady.



import Script from "next/script";

// Importing useEffect
import { useEffect } from "react";

import hljs from "highlight.js/lib/core";

import sql from "highlight.js/lib/languages/sql";
import javascript from "highlight.js/lib/languages/javascript";
import c from "highlight.js/lib/languages/c";
import css from "highlight.js/lib/languages/css";
import scss from "highlight.js/lib/languages/scss";
import shell from "highlight.js/lib/languages/shell";
import python from "highlight.js/lib/languages/python";
import powershell from "highlight.js/lib/languages/powershell";
import cpp from "highlight.js/lib/languages/cpp";
import php from "highlight.js/lib/languages/php";
import phpTemplate from "highlight.js/lib/languages/php-template";
import xml from "highlight.js/lib/languages/xml";

const post = ({ post }) => {
  // Registering languages
  useEffect(() => {
    hljs.registerLanguage("sql", sql);
    hljs.registerLanguage("javascript", javascript);
    hljs.registerLanguage("python", python);
    hljs.registerLanguage("c", c);
    hljs.registerLanguage("cpp", cpp);
    hljs.registerLanguage("powershell", powershell);
    hljs.registerLanguage("shell", shell);
    hljs.registerLanguage("scss", scss);
    hljs.registerLanguage("css", css);
    hljs.registerLanguage("php", php);
    hljs.registerLanguage("php-template", phpTemplate);
    hljs.registerLanguage("html", xml);
    hljs.registerLanguage("xml", xml);
  });

  return (
    <>
      <Script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></Script>
      {/* Import highlight js */}
      <div>{/* Post content goes here */}</div>
    </>
  );
};

Final step

We have successfully registered all the languages now final step is to highlight the code. for that we'll be using highlightAll() function from the hljs means Highlight.Js

We'll be wrapping the highlightAll() function inside useEffect() so that it highlight only when window is loaded.

[slug].js



useEffect(() => {
  hljs.highlightAll({ detectLanguage: true });
});

And that's it! Our final code should look like this



import Script from "next/script";

// Importing useEffect

import { useEffect } from "react";

import hljs from "highlight.js/lib/core";

import sql from "highlight.js/lib/languages/sql";

import javascript from "highlight.js/lib/languages/javascript";

import c from "highlight.js/lib/languages/c";

import css from "highlight.js/lib/languages/css";

import scss from "highlight.js/lib/languages/scss";

import shell from "highlight.js/lib/languages/shell";

import python from "highlight.js/lib/languages/python";

import powershell from "highlight.js/lib/languages/powershell";

import cpp from "highlight.js/lib/languages/cpp";

import php from "highlight.js/lib/languages/php";

import phpTemplate from "highlight.js/lib/languages/php-template";

import xml from "highlight.js/lib/languages/xml";

const post = ({ post }) => {

  // Registering languages

  useEffect(() => {

    hljs.registerLanguage("sql", sql);

    hljs.registerLanguage("javascript", javascript);

    hljs.registerLanguage("python", python);

    hljs.registerLanguage("c", c);

    hljs.registerLanguage("cpp", cpp);

    hljs.registerLanguage("powershell", powershell);

    hljs.registerLanguage("shell", shell);

    hljs.registerLanguage("scss", scss);

    hljs.registerLanguage("css", css);

    hljs.registerLanguage("php", php);

    hljs.registerLanguage("php-template", phpTemplate);

    hljs.registerLanguage("html", xml);

    hljs.registerLanguage("xml", xml);

  });

useEffect(() => {

    hljs.highlightAll({ detectLanguage: true });

  });

return (

    <>

      <Script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/11.9.0/highlight.min.js"></Script>

      {/* Import highlight js /}

      <div>{/ Post content goes here */}</div>

    </>

  );

};

export default post;

Wrapping up

So that was it for this blog. If you get any issues or need any help feel free to post comment or reaching me on LinkedIn or Mail

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