Introduction to mdast

mdast stands for Markdown Abstract Syntax Tree, a powerful tool for parsing markdown content into a structured tree format. This enables advanced manipulation and analysis of markdown documents. Below, we will cover some key APIs provided by the mdast library with practical code examples.

API Overview and Code Snippets

1. parse Method

The parse method converts markdown text into an abstract syntax tree.

const unified = require('unified');
const parse = require('remark-parse');

const file = '## Sample Markdown\nThis is a paragraph.';
const tree = unified().use(parse).parse(file);
console.log(tree);
    

2. stringify Method

The stringify method converts an abstract syntax tree back into markdown text.

const unified = require('unified');
const stringify = require('remark-stringify');

const tree = {
    type: 'root',
    children: [
        {type: 'heading', depth: 2, children: [{type: 'text', value: 'Sample Markdown'}]},
        {type: 'paragraph', children: [{type: 'text', value: 'This is a paragraph.'}]}
    ]
};
const file = unified().use(stringify).stringify(tree);
console.log(file);
    

3. visit Method

The visit method allows traversing nodes in the abstract syntax tree.

const unified = require('unified');
const parse = require('remark-parse');
const visit = require('unist-util-visit');

const file = '## Sample Markdown\nThis is a paragraph.';
const tree = unified().use(parse).parse(file);

visit(tree, 'text', (node) => {
  console.log(node.value);
});
    

4. transform Method

The transform method for modifying the syntax tree.

const unified = require('unified');
const parse = require('remark-parse');
const transform = require('remark-rehype');

const file = '## Sample Markdown\nThis is a paragraph.';
const processor = unified()
  .use(parse)
  .use(transform);
const tree = processor.parse(file);
const newTree = processor.runSync(tree);
console.log(newTree);
    

Application Example

Here is an example application showcasing the use of mdast APIs to parse, transform, and stringify markdown content.

const unified = require('unified');
const parse = require('remark-parse');
const stringify = require('remark-stringify');
const visit = require('unist-util-visit');
const transform = require('remark-rehype');

const file = '# Title\n\nSome **bold** text and a [link](#).';

const processor = unified()
  .use(parse)
  .use(transform)
  .use(() => (tree) => {
      visit(tree, 'link', (node) => {
        node.url = 'https://example.com';
      });
      return tree;
    })
  .use(stringify);

const result = processor.processSync(file);
console.log(String(result));
    

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