Highlight code with Markdown-it.js and Highlight.js

Question

In the current example, a Markdown snippet is ported to HTML and the output is shown in the DIV (ID Content).

The highlight function (hljs.highlight) is set to the options markdown-it (md). However, this is not carried out.

What do I have to change so that the output uses the highlight.js?

<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8"/>
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/highlightjs/cdn-release@10.2.1/build/styles/default.min.css">
    <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/markdown-it/11.0.1/markdown-it.min.js "></script>
    <script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.2.1/highlight.min.js"></script>
</head>
<body>
    <div id="content"></div>


    <script>
    var md = window.markdownit();
    md.set({
      highlight: function (str, lang) {
        if (lang && hljs.getLanguage(lang)) {
          try {
            return '<pre class="hljs"><code>' +
                   hljs.highlight(lang, str, true).value +
                   '</code></pre>';
          } catch (__) {}
        }

        return '<pre class="hljs"><code>' + md.utils.escapeHtml(str) + '</code></pre>';
      }
    });

    var result = md.render('# markdown-it rulezz! \n\n```html <pre><code class="js">function test();</code></pre>```');
    document.getElementById('content').innerHTML = result;
    </script>

    
</body>
</html>

https://github.com/markdown-it/markdown-it/blob/master/support/demo_template/index.js you could dig src of web demo, it works. — Vitaly, Oct 16 '20 at 18:42

Thiago Bernardi · Accepted Answer · 2021-04-22T21:22:15.633

Hope it's not too late.

You must break line (\n) after your fenced code block.

So this:

var result = md.render('# markdown-it rulezz! \n\n```html <pre><code class="js">function test();</code></pre>```');

Should be:

var result = md.render('# markdown-it rulezz! \n\n ```html \n <pre><code class="js">function test();</code></pre>\n```');

This is how everything should be:

the .js files should be:

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/markdown-it/11.0.1/markdown-it.min.js "></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/highlight.js/10.2.1/highlight.min.js"></script>

These are okay.
As for the .css, you can use the one you are using or you can use the one that is in the npm:
npm install markdown-it-highlight
get the .css file at node_modules/markdown-it-highlight/dist/index.css, that has nicer syntax highlighting color and use that.

Then you would have to set this defaults object and set this on the defaults.highlight:

var defaults = {
    html: false, // Enable HTML tags in source
    xhtmlOut: false, // Use '/' to close single tags (<br />)
    breaks: false, // Convert '\n' in paragraphs into <br>
    langPrefix: 'language-', // CSS language prefix for fenced blocks
    linkify: true, // autoconvert URL-like texts to links
    typographer: true, // Enable smartypants and other sweet transforms
    // options below are for demo only
    _highlight: true, // <= THIS IS WHAT YOU NEED
    _strict: false,
    _view: 'html' // html / src / debug
};

// and then do this:

defaults.highlight = function (str, lang) {
    var esc = md.utils.escapeHtml;
    console.log(str)
    console.log(lang)
    if (lang && hljs.getLanguage(lang)) {
      try {
        return '<pre class="hljs"><code>' +
               hljs.highlight(lang, str, true).value +
               '</code></pre>';
      } catch (__) {}
    }else{
      return '<pre class="hljs"><code>' + esc(str) + '</code></pre>';
    }

};

// now set the md:

md = window.markdownit(defaults);

// now this is where you forgot the line break after the fenced code block:

const result = md.render('# markdown-it rulezz! \n ```html \n <pre><code class="js">function test();</code></pre>\n```');

document.querySelector('#content').innerHTML = result;

score 0 · Answer 2 · answered Dec 19 '22 at 19:58

I outlined a few of the steps needed to get code highlighting working here: https://github.com/microsoft/AdaptiveCards/discussions/8081#discussioncomment-4219420

Summary:

Easy Way

First, make sure you support Markdown in cards:

import MarkdownIt from 'markdown-it'

// For Markdown in Adaptive Cards.
window.markdownit = MarkdownIt

Now we'll use another library to color code:

import highlight from 'highlight.js'
import 'highlight.js/styles/github.css'

Run:

highlight.highlightAll()

to update all your cards.

If you run it twice, then it will try to update cards that it already updated, and you'll get warnings. See https://github.com/microsoft/AdaptiveCards/discussions/8081#discussioncomment-4219420 for handling dynamically added cards.

Highlight code with Markdown-it.js and Highlight.js

2 Answers2

This is how everything should be:

Easy Way