name : maintaining-cjs-module-lexer.md # Maintaining cjs-module-lexer The [cjs-module-lexer](https://github.com/nodejs/node/tree/HEAD/deps/cjs-module-lexer) dependency is used within the Node.js ESM implementation to detect the named exports of a CommonJS module. It is used within [`node:internal/modules/esm/translators`](https://github.com/nodejs/node/blob/HEAD/lib/internal/modules/esm/translators.js) in which both `internal/deps/cjs-module-lexer/lexer` and `internal/deps/cjs-module-lexer/dist/lexer` are required and used. `internal/deps/cjs-module-lexer/lexer` is a regular JavaScript implementation that is used when WebAssembly is not available on a platform. `internal/deps/cjs-module-lexer/dist/lexer` is a faster implementation using WebAssembly which is generated from a C based implementation. These two paths resolve to the files in `deps/cjs-module-lexer` due to their inclusion in the `deps_files` entry in [node.gyp](https://github.com/nodejs/node/blob/main/node.gyp). The two different versions of lexer.js are maintained in the [nodejs/cjs-module-lexer][] project. In order to update the Node.js dependencies to use to a newer version of cjs-module-lexer, complete the following steps: * Clone [nodejs/cjs-module-lexer][] and check out the version that you want Node.js to use. * Follow the WASM build steps outlined in [wasm-build-steps](https://github.com/nodejs/cjs-module-lexer#wasm-build-steps). This will generate the WASM based dist/lexer.js file. * Preserving the same directory structure, copy the following files over to `deps/cjs-module-lexer` directory where you have checked out Node.js. ```text ├── CHANGELOG.md ├── dist │ ├── lexer.js │ └── lexer.mjs ├── lexer.js ├── LICENSE ├── package.json └── README.md ``` * Update the link to the cjs-module-lexer in the list at the end of [doc/api/esm.md](../../api/esm.md) to point to the updated version. * Create a PR, adding the files in the deps/cjs-module-lexer that were modified. If updates are needed to cjs-module-lexer for Node.js, first PR those updates into [nodejs/cjs-module-lexer][], request a release and then pull in the updated version once available. [nodejs/cjs-module-lexer]: https://github.com/nodejs/cjs-module-lexer