Using npm link to test a module locally

When you're developing an NPM package, there's a problem that quickly becomes frustrating:

Every time you modify the module, you would normally have to:

• publish a new version
• reinstall the package in the test project
• restart the application

Fortunately, npm link exists precisely to avoid this.

How it works

This command lets you create a symbolic link between a local package and another project.

In other words: your project directly uses the local source code of the module, as if it had been installed from NPM.

The process happens in two steps. First, in the NPM package folder:

npm link

This command registers the package globally on your machine.

Then, in the project that needs to use this package:

npm link nom-du-package

From that point on, the project's node_modules folder will point directly to your local module.

A symbolic link

The big advantage is that changes become almost instantaneous. You change code in your package… and your test project immediately uses the new version.

No more need to publish a 0.0.1-dev-test-42 version.

Under the hood, npm link uses the operating system's symbolic links (symlink).

A concrete example

Here's an example to clearly understand the steps to follow. You have two projects:

mon-package/
mon-app/

npm link

npm link mon-package

And there you go. Your application now directly uses the local version of the package.