Markdown-it: Elegant Markdown Parser for Developers

Markdown-it is a powerful, pluggable Markdown parser that provides an extensive set of features and APIs, making it a preferred choice for developers. This article introduces Markdown-it and dives into its numerous useful APIs with practical code snippets to help you make the most out of it.

Getting Started with Markdown-it

To start using Markdown-it, you need to install it via npm:

npm install markdown-it --save

Basic Usage

Here’s a basic example of how you can use Markdown-it to convert Markdown to HTML:

const MarkdownIt = require('markdown-it');
const md = new MarkdownIt();
const result = md.render('# Markdown-it rulezz!');
console.log(result);

Advanced APIs

Use Plugins

Markdown-it allows you to extend its functionality using plugins:

const md = require('markdown-it')()
  .use(require('markdown-it-emoji'));
console.log(md.render('I :heart: Markdown-it!'));

Custom Ruler

If you need custom rules, you can define and apply them:

const md = new MarkdownIt();
md.core.ruler.push('foo', function(state) {
  console.log('Hello from custom rule!');
});

Token Modification

You can manipulate tokens directly:

md.core.ruler.before('linkify', 'replace-class', function replace(state) {
  state.tokens.filter(token => token.type === 'link_open').forEach(token => {
    var index = token.attrIndex('class');
    if (index < 0) {
      token.attrPush(['class', 'new-class']);
    } else {
      token.attrs[index][1] = 'new-class';
    }
  });
});

Inline Ruler

Custom inline rules can be defined as well:

md.inline.ruler.before('emphasis', 'example', function customRule(state, silent) {
  if (state.src.charCodeAt(state.pos) !== 0x40 /* @ */) return false;
  if (silent) return false;
  const match = state.src.slice(state.pos).match(/^@example/);
  if (!match) return false;
  state.pos += match[0].length;
  state.push({ type: 'text', content: 'example content' });
  return true;
});

Markdown-it Application Example

Below is an example of an application using several Markdown-it features:

const express = require('express');
const MarkdownIt = require('markdown-it');
const emoji = require('markdown-it-emoji');

const app = express();
const md = new MarkdownIt().use(emoji);

app.use(express.json());

app.post('/convert', (req, res) => {
  const result = md.render(req.body.markdown);
  res.send(result);
});

app.listen(3000, () => console.log('Server is running on port 3000'));

This application sets up an Express server that receives Markdown input through a POST request and converts it to HTML using Markdown-it and the emoji plugin.

Markdown-it is a flexible and powerful tool for developers who need a robust Markdown parser. With its extensive APIs and plugin system, it can be tailored to fit a wide variety of use cases.

Happy coding with Markdown-it!

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