If you want to develop your own npm package, you first have to test it locally.

I had this need with a project that I wanted to modularize.

I had a package I called, as an example, flaviocopes-common-database.

I prepended flaviocopes- to give it a unique namespace.

Inside the package I added a package.json file with the module name in the name property and a few dependencies:

{
  "name": "flaviocopes-common-database",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "dependencies": {
    "pg": "^8.0.2",
    "sequelize": "^5.21.6"
  }
}

Then I ran

npm link

This created a symbolic link in the /usr/local/lib/node_modules/ folder, that contains the global npm packages in the system, the ones installed using npm -g, to be clear.

I had

/usr/local/lib/node_modules/flaviocopes-common-database

Pointing to the local file I had in

/Users/flavio/dev/code/flaviocopes-common-database

Now in another project I wanted to use this module, so I ran

npm link flaviocopes-common-database

and I was able to import it in the Node.js code using the usual require() syntax:

const database = require('flaviocopes-common-database')

Lessons in this unit:

0:	Introduction
1:	How to use or execute a package installed using npm
2:	npm dependencies and devDependencies
3:	How to fix the "Missing write access" error when using npm
4:	npm can install packages in the parent folder
5:	Install an older version of an npm package
6:	Find the installed version of an npm package
7:	▶︎ How to test an npm package locally
8:	npm global or local packages
9:	What are peer dependencies in a Node module?
10:	`npm run dev` is a long-running program
11:	Semantic Versioning using npm
12:	Uninstalling npm packages with `npm uninstall`
13:	An introduction to the npm package manager
14:	The npx Node Package Runner
15:	The package.json guide
16:	The package-lock.json file
17:	What is pnpm?
18:	Should you commit the node_modules folder to Git?
19:	Update all the Node dependencies to their latest version
20:	Where does npm install the packages?
21:	Bumping Node.js dependencies
22:	Run package.json scripts upon any file changes in a folder