@willbooster/tree-sitter-javascript

JavaScript and JSX grammar for tree-sitter, forked from tree-sitter/tree-sitter-javascript. We are grateful to its authors and contributors. This is not an official release of that project.

This fork fixes parsing bugs and raises conformance with ECMAScript (ECMA-262) and JSX.

Usage

The npm package ships tree-sitter-javascript.wasm for web-tree-sitter:

import { fileURLToPath } from 'node:url';
import { Language, Parser } from 'web-tree-sitter';

await Parser.init();
const parser = new Parser();
const wasmPath = fileURLToPath(import.meta.resolve('@willbooster/tree-sitter-javascript/tree-sitter-javascript.wasm'));
parser.setLanguage(await Language.load(wasmPath));
const tree = parser.parse('const App = () => <p>Hello</p>;\n');

The package also ships the node types in src/node-types.json.

In Rust, depend on the crate:

[dependencies]
tree-sitter = "0.27"
tree-sitter-javascript = { package = "willbooster-tree-sitter-javascript", version = "1" }

let mut parser = tree_sitter::Parser::new();
parser.set_language(&tree_sitter_javascript::LANGUAGE.into())?;

Development

mise install
bun install --frozen-lockfile
bun run build/ci
bun run test
script/parse-examples
cargo test

bun run test runs:

• the corpus in test/corpus, with the native build and with the Wasm build (the first run downloads the WASI SDK);
• an incremental-parsing check (test/unit/incremental.test.ts): tree-sitter fuzz edits each corpus case at random, reparses it, undoes the edits, and reparses again. TREE_SITTER_SEED, TREE_SITTER_ITERATIONS, and TREE_SITTER_EDITS run other or more edits;
• a check that the real-world JavaScript files in examples/, the checked-in ones and those of the cloned repository, fail to parse exactly as listed in script/known-failures.txt. The first run clones the repository. The example repository is pinned to a commit in script/parse-examples. After a grammar change or a moved pin alters that list, script/parse-examples rewrites it; review its diff before committing;
• a performance check (test/unit/performance.test.ts) that recovering from an error on each of 10,000 lines takes linear time, since consumers parse files while they are being edited. It loads the Wasm build through web-tree-sitter, which bun run build/ci rebuilds after regenerating the parser.

CI also runs these tests on Linux arm64 and macOS, where the Rust binding compiles the parser natively, and fuzzes the parser with libFuzzer and sanitizers (.github/workflows/robustness.yml).

References

• The ESTree Spec
• The ECMAScript 2025 Spec