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Lanexio Parser Lanexio Parser

Quick Start

This page gets you from installation to first useful output. If you haven’t installed yet, start with Installation.

Parse HTML

Section titled “Parse HTML”
import { parseHtml } from '@lanexio/parser-grammar-html';


const encoder = new TextEncoder();
const tree = parseHtml(encoder.encode('<p>Hello <strong>world</strong></p>'));


console.log(tree.nodeCount);   // total nodes in the flat AST
console.log(tree.root.kind);   // numeric kind id for the Document root

parseHtml accepts a Uint8Array, not a string. Use TextEncoder to convert. It always returns a LexTree and never throws, even on malformed input.

Parse Markdown

Section titled “Parse Markdown”
import { parseMarkdown } from '@lanexio/parser-grammar-markdown';


const encoder = new TextEncoder();
const tree = parseMarkdown(encoder.encode('# Hello\n\nA **bold** paragraph.'));


console.log(tree.nodeCount);
console.log(tree.root.kind);

GFM (GitHub Flavored Markdown) extensions are enabled by default. Pass { gfm: false } to restrict to CommonMark only.

Parse JSON

Section titled “Parse JSON”
import { parseJson } from '@lanexio/parser-grammar-json';


const encoder = new TextEncoder();
const tree = parseJson(encoder.encode('{"key": [1, true, null]}'));


console.log(tree.nodeCount);   // total nodes in the flat AST
console.log(tree.root.kind);   // numeric kind id for the Document root

parseJson implements RFC 8259. It accepts a Uint8Array, never throws, and passes 375/375 JSONTestSuite cases (95 accept, 183 reject, 33 never-throw).

Parse YAML

Section titled “Parse YAML”
import { parseYaml } from '@lanexio/parser-grammar-yaml';


const encoder = new TextEncoder();
const tree = parseYaml(encoder.encode('key: value\nlist:\n  - one\n  - two'));


console.log(tree.nodeCount);
console.log(tree.root.kind);

parseYaml implements YAML 1.2.2 including flow collections ({...}, [...]), anchors, aliases, and tags. 267/268 yaml-test-suite valid cases pass.

Traverse the tree

Section titled “Traverse the tree”
import { parseHtml } from '@lanexio/parser-grammar-html';
import { HtmlKind } from '@lanexio/parser-grammar-html';


const encoder = new TextEncoder();
const tree = parseHtml(encoder.encode('<ul><li>one</li><li>two</li></ul>'));
const cursor = tree.cursor();


do {
  const node = cursor.current;
  const src = tree.source;
  const text = new TextDecoder().decode(src.subarray(node.range.start, node.range.end));
  console.log(node.kind, JSON.stringify(text.slice(0, 40)));
} while (cursor.gotoFirstChild() || cursor.gotoNextSibling() || cursor.gotoParent());

Check for errors

Section titled “Check for errors”
import { parseHtml } from '@lanexio/parser-grammar-html';


const encoder = new TextEncoder();
const tree = parseHtml(encoder.encode('<p><strong>unclosed'));


for (const node of tree.root.children()) {
  if (node.hasError) {
    console.log('LexError at', node.range);
  }
}

parseHtml never throws. Malformed input produces LexError nodes in the tree. You can detect and report them, or ignore them, depending on your use case.

Next steps

Section titled “Next steps”