react-refractor

react-refractor

Syntax highlighter for React, utilizing VDOM for efficient updates

• Thin wrapper on top of refractor (Syntax highlighting using VDOM)
• refractor uses Prism under the hood, thus supports all the same syntaxes
• About 14kB minified + gziped when using a single language syntax. Languages tend to add a bit of weight, see unpkg for some pointers on how much.

Feel free to check out a super-simple demo.

Installation

This package is ESM only and requires React 18 or higher.

npm install --save react-refractor

Usage

import {Refractor, registerLanguage} from 'react-refractor'

// Load any languages you want to use from `refractor`
import js from 'refractor/lang/javascript.js'
import php from 'refractor/lang/php.js'

// Then register them
registerLanguage(js)
registerLanguage(php)

ReactDOM.render(
  <Refractor language="js" value="/* Code to highlight */" />,
  document.getElementById('target'),
)

You'll need to register the languages you want to use - I've intentionally left all languages out of the default bundle in order to reduce the bundle size out of the box. Load and register them from refractor using something like this:

import docker from 'refractor/lang/docker'

registerLanguage(docker)

Styling

Stylesheets are not automatically handled for you - but there is a bunch of premade themes for Prism which you can simply drop in and they'll "just work". You can either grab these from the source, of pull them in using a CSS loader - whatever works best for you. You can also download a customized stylesheet from Prism's download customizer.

Note that when using the markers feature, there is an additional class name called hljs-marker which is not defined by highlight js as it's not a part of its feature set. You can either set it yourself, or you can explicitly set class names on markers.

Props

Name	Description
className	Class name for the outermost pre tag. Default: refractor
language	Language to use for syntax highlighting this value. Must be registered prior to usage
value	The code snippet to syntax highlight
inline	Whether code should be displayed inline (no <pre> tag, sets display: inline)
markers	Array of lines to mark. See section on markers below
plainText	Set to true to skip highlighting and render the passed value as-is

Differences to Prism

Prism.js operates directly on the DOM, while refractor generates an AST which react-refractor walks over and converts into virtual DOM nodes. The benefit of the AST approach is that we can easily reuse this across different platforms, highlight on both the server and the client using the same code base and benefit from Reacts virtual DOM diff algorithm to only update the nodes that change.

The drawback to this approach is that you cannot use Prism plugins, since they also work and depend directly on the DOM.

Markers

It's quite common to want to highlight lines when doing syntax highlighting, but Prism uses a very DOM-centric approach to achieve this. In order to make up for this, react-refractor provides a custom plugin that lets you define "markers". Since this is a non-standard feature, you will have to provide your own styling for the refractor-marker class name. To highlight lines, simply provide the line numbers in the markers property:

const source = `
const foo = 'bar'
const bar = 'foo'
const baz = foo + bar
`

// Highlight line 1 and 2, but not 3
<Refractor
  language="js"
  value={source}
  markers={[1, 2]}
/>

You are also able to provide greater customization by specifying an object for each marker, which can include either a className or a component property. This allows you to render basically anything you want:

const source = `
const foo = 'bar'
const bar = 'foo'
const baz = "bar" + bar
`

// Highlight line 1 and 2, but not 3
<Refractor
  language="js"
  value={source}
  markers={[
    {line: 1, className: 'no-not-use-foo-in-examples'},
    {line: 3, component: props => (
      <TooltipedLine tooltipText="Prefer template for string concatenation">
        {props.children}
      </TooltipedLine>
    )}
  ]}
/>

License

MIT-licensed. See LICENSE.