This article will show you how to use npm link to share code to others projects locally.

Source code

Motivation

Sometime you want to extract code to become a shared library to make it reuseable. If you are nodejs developer, you probably want to make it as a node module, so you can use the same behavoir to load the library. However, you mightn’t want to publish the library to public, you can use npm-link to publish the library locally.

what is npm-link, see https://docs.npmjs.com/cli/link

Basically, npm-link is create symlink the project, you want to share, in the npm folder, also the other project create other symlinks connect to that folder. So when you make a change, it affect other projects immediately(you don’t need to use npm update to update)

Example

In the repo, there are three projects. the sharedlib is the one want to share. And proejct1 and project2 want to use sharedlib.

First in the sharedlib folder, run

~/Projects/shreadlib> npm link

# output
C:\Users\Wade\AppData\Roaming\npm\node_modules\sharedlib -> C:\Users\Wade\Projects\sharedlib

you can see npm create a symlink in its package folder.

Then in the project1 folder, run

~\Projects\project1> npm link sharedlib

# output
C:\Users\Wade\Projects\project1\node_modules\sharedlib ->
C:\Users\Wade\AppData\Roaming\npm\node_modules\sharedlib -> 
C:\Users\Wade\Projects\sharedlib

Then in the project2 folder, run

~\Projects\project2> npm link sharedlib

# output
C:\Users\Wade\Projects\project2\node_modules\sharedlib ->
C:\Users\Wade\AppData\Roaming\npm\node_modules\sharedlib -> 
C:\Users\Wade\Projects\sharedlib

you can see all node_modules\sharedlib are link to ~\Projects\sharedlib. This is why changes affect other projects immediately, becasue they are pointer the same places in the hard disk.

pros and cons

You can publish libraries locally and the libraries are updated instantly. Unlike public libraies, you have to push and pull the a server. Also there is another benefit, you can simplify the path of require.

For example,

// because sharedlib is under the ./model_modules, so you don't need to use relative path.
var lib = require("sharedlib");

However, the linked packages aren’t define in package.json. so other people want to start working on the project, they have to run npm-link manually at first.

npm-unlink

you can run npm unlink to remove the symlimks.