[Node.js] Using npm link to use node modules that are "in progress"

It is some times convenient, even necessary, to make use of a module that you are working on before it has been published to the node package manager (npm). The npm link command makes this simple.

For example:

upper/index.js:

module.exports = function(str){
    return str.toUpperCase();
}

packjson:

{
  "name": "upper",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo "Error: no test specified" && exit 1"
  },
  "author": "",
  "license": "ISC"
}

user/index.js:

var upper = require('upper');

console.log(upper('hello world'));

In the user/index.js, we want to use upper module which is not published to the npm yet. Therefore, when we run the app, it will report the error:

Enable to test the module, we can use 'npm link':

1. Locate upper folder and run:

npm link

It says that our node_modules links to this upper module.

[Notice:] You need to have package.json file when using 'npm link', because it uses its name to refering the module.

　　2. Go back to the user dir, use that upper dir:

cd ../user

npm link upper

C:UsersAnswer1215WebstormProjectsmean
pmlinkuser
ode_modulesupper -> C:UsersAnswer1215AppDataRoaming
pm
ode_modulesupper -> C:UsersAnswer1215WebstormProjectsmean

pmlinkupper

It says that, our upper dir links to the system node_module's upper, then links to our user dir.

　　3. Now we can use this upper module.

[Notice:] Once you finish testing, you need to unlink this moduole! or it may cause problem

　　4. In the user dir:

npm unlink upper

More:

https://egghead.io/lessons/node-js-using-npm-link-to-use-node-modules-that-are-in-progress