Overview

This is currently just an unstable side project where I'm trying to use PrismJs, but as a pure function.

Usage

First, install prism-functional from npm:

npm install prism-functional

Import the module, import the language you need, and run the function on the code you need to highlight.

import prism from "prism-functional"
import langJavascript from "prism-functional/languages/javascript

const codeSnippet = 'console.log("Hello world!")'
const highlightedHtml = prism(codeSnippet, langJavascript)
console.log(highlightedHtml)
// console<span class="token punctuation">.</span><span class="token function">log</span><span class="token punctuation">(</span><span class="token string">"Hello world!"</span><span class="token punctuation">)</span>

Available Languages

I've copy-pasta'd the following languages from Prism's source. The original language files have to be modified slightly to declare and export the grammar rather than append it to the global Prism object. In addition, many languages use properties of the global Prism object, such as Prism.languages.extend. These had to be replaced with more pure-function-like versions.

The following languages can be imported immediately:

// bash
import lang_bash from "prism-functional/languages/bash";
// clike
import lang_clike from "prism-functional/languages/clike";
// ebnf
import lang_ebnf from "prism-functional/languages/ebnf";
// go (extends "clike")
import lang_go from "prism-functional/languages/go";
// hcl (hashicorp configuration language)
import lang_hcl from "prism-functional/languages/hcl";
//  javascript (extends "clike")
import lang_javascript from "prism-functional/languages/javascript";
//  sentinel (extends "clike")
import lang_sentinel from "prism-functional/languages/sentinel";
//  shell-session (uses "bash")
import lang_shell_session from "prism-functional/languages/shell-session";

So far, moving languages over has been a relatively straightforward and quick task. Ideally, I'd find a way to use the Prism source directly somehow rather than copying-and-pasting it, but frankly I don't know enough about javascript to even know whether that would be possible 😬

Plugins and hooks

The proper version of PrismJS seems to have a very robust plugin ecosystem. I have not attempted to recreate it in this "functional" version. I think it's probably possible, but I have much less experience with this kind of implementation, so I'm honestly not sure. I also haven't yet felt an acute need to use plugins.

Background

I was curious how PrismJS could be used in as simple of a way as possible, in a portable way. For example, I wanted to be able to use Prism to highlight code when processing markdown, and also wanted to use it in a React component. I found it challenging to do these things - it seems like typical usage is targeted at running Prism in the browser.

However, I didn't want to give up on Prism - I really like how lightweight it is, and I really like the number of languages available, and the tools for defining new language grammars.

I feel more familiar with functional programming paradigms, and the more I thought about, the more I landed on wanting to use Prism like this:

const highlightedHtml = prism(code, language);

This led me towards trying to lazily adapt PrismJS to meet this need. I've basically just tried to recreate Prism.highlight in a more pure-function-ish way.