@lezer/javascript

lezer-based JavaScript grammar

0.15.3
Source
npm

Version published: 3 years ago

Maintainers: 1

Created: 3 years ago

What is @lezer/javascript?

@lezer/javascript is a parser for JavaScript written using the Lezer parser system. It provides a way to parse JavaScript code into a syntax tree, which can be used for various purposes such as syntax highlighting, code analysis, and transformation.

What are @lezer/javascript's main functionalities?

Parsing JavaScript Code

This feature allows you to parse JavaScript code into a syntax tree. The code sample demonstrates how to parse a simple JavaScript statement and print the resulting syntax tree.

const {parser} = require('@lezer/javascript');
const input = 'const x = 10;';
const tree = parser.parse(input);
console.log(tree.toString());

Syntax Tree Traversal

This feature allows you to traverse the syntax tree. The code sample shows how to use a TreeCursor to iterate over the nodes in the syntax tree and print their types.

const {parser} = require('@lezer/javascript');
const {TreeCursor} = require('@lezer/common');
const input = 'const x = 10;';
const tree = parser.parse(input);
let cursor = tree.cursor();
do {
  console.log(cursor.node.type.name);
} while (cursor.next());

Custom Syntax Highlighting

This feature allows you to apply custom syntax highlighting to JavaScript code. The code sample demonstrates how to define a highlighting style and apply it to a parsed syntax tree.

const {parser} = require('@lezer/javascript');
const {highlightTree} = require('@lezer/highlight');
const {styleTags, tags} = require('@lezer/highlight');
const input = 'const x = 10;';
const tree = parser.parse(input);
const highlightStyle = styleTags({
  'VariableName': tags.variableName,
  'Keyword': tags.keyword,
  'Number': tags.number
});
let highlighted = '';
highlightTree(tree, highlightStyle, (from, to, classes) => {
  highlighted += input.slice(from, to) + ' [' + classes + '] ';
});
console.log(highlighted);

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