Do you know how to link local dependency for npm?

When working on multiple related JavaScript projects, you may need to test changes in a local dependency without publishing it to npm. npm link provides a way to symlink a local package, allowing real-time updates without reinstalling the package manually. However, improper usage can lead to issues like dependency mismatches or unresolved modules.

How npm link works

npm link creates a symbolic link between a globally registered local package and a project that depends on it.

Steps to link a local dependency

1. Navigate to the local package directory (the dependency you are developing) and run:

   npm link

   This registers the package globally on your system.

2. Navigate to the project that will use this dependency and run:

   npm link <package-name>

   This links the globally registered package into your project’s node_modules.

Example usage

If you're developing my-local-package and want to use it in another project:

cd ~/projects/my-local-package
npm link
cd ~/projects/my-app
npm link my-local-package

Now, my-app will use the local version of my-local-package instead of fetching it from npm.

Common issues and fixes

• Module Resolution Issues: If your project uses a different version of a peer dependency than the linked package, you might get errors. A common fix is running:

  npm install

  in both the linked package and the main project.

• TypeScript Not Detecting Changes: Sometimes, TypeScript may not immediately recognize changes in a linked package. Restarting the TypeScript server (tsc --watch) or adding "preserveSymlinks": true in tsconfig.json can help.

Alternatives to npm link

1. Using npm install <path>

Instead of linking, you can install a local package directly:

npm install ../my-local-package

2. Using npm pack

Another option is to create a tarball of the package and install it manually:

cd my-local-package
npm pack
npm install ../my-local-package/my-local-package-1.0.0.tgz

Best practices

• Use npm link mainly for development, not for production environments
• Always verify dependencies are correctly installed after linking
• Consider npm install <path> or npm pack if npm link causes issues

By understanding and properly using npm link, you can streamline local package development while avoiding common pitfalls.