Syntax highlight any block on a Web Page

May 27, 2022

Learn how to syntax highlight any element on a web page with highlight.js and hljs.highlightElement, even when your code is not inside a code tag.

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I had the need to add syntax highlighting to a page, but I didn’t have the luxury of changing the markup.

Most syntax highlighting libraries, like Prism.js, force you to use a fixed structure like this:

<pre>
  <code class="language-js">
    ...
  </code>
</pre>

Citing this:

Prism does its best to encourage good authoring practices. Therefore, it only works with elements, since marking up code without a element is semantically invalid.


It’s all nice and idealistic and all but I had my code in a div from an outside source. You force me that markup, but I don’t have that.
I finally found https://highlightjs.org/ that lets me apply syntax highlighting to any element I want on the page, by loading the library first and then calling:
document.addEventListener('DOMContentLoaded', () => {
  document.querySelectorAll('.my-code-div').forEach((el) => {
    hljs.highlightElement(el)
  })
})

Tagged: Tools · All topics

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