NPM manages dependencies for a NodeJS applications. NPM gets installed with NodeJS when installing with an installer or you can install with a single line.

~$curl | sh

Lets start from scratch with a basic application

~$mkdir MyNodePrjt
~$cd MyNodeProject

MyNodePrjt-$touch app.js

Lets say that we require installing a node module called express, which is a simple MVC web framework for NodeJS. We can do that using npm install module_name. Now the module will be installed for this project. If you need to make a global installation you will need to add a parameter -g

MyNodePrjt-$npm install express
MyNodePrjt-$npm install -g express

If you are particular about certain version of the module

MyNodePrjt-$npm install [email protected] For uninstalling a module

MyNodePrjt-$npm uninstall express

Don’t you think this is painful to install everytime all the required modules for your project when ever you change your system or for your colleague who is working on the same repository using GIT or SVN! To solve this like all other package managers we have a configuration file named package.json. In fact, you don’t need to take the pain of creating the file and maintain it for every change in the dependency modules. You can create for this existing project by typing npm init

MyNodePrjt-$npm init

After few interactive questions it will generate the json file with contents

  "name": "MyNodePrjt",
  "version": "0.0.1",
  "description": "This is my first NodeJS Project",
  "main": "app.js",
  "dependencies": {
    "express": "~3.4.8"
  "devDependencies": {},
  "scripts": {
  	"start": "node app.js"
    "test": "echo \"Error: no test specified\" && exit 1"
  "author": "Prakash",
  "license": "MIT"

The contents above are readable. dependencies section is for dependencies of the project but devDependencies are dependencies during the development environment where you can use advanced debugging, logging or may be simulation test modules. scripts can be executed using npm to perform tasks like start the server, run the tests, things to do on postInstall etc.,

To start the server, with out concerning about the parameters you pass or file to run just run npm start

MyNodePrjt-$npm start
MyNodePrjt-$npm test

Once this is generated everytime you are installing a new module you will need to use add a parameter ‘–save’ to save in the dependencies and ‘–save-dev’ to save in the devDependencies

MyNodePrjt-$npm install jade --save
MyNodePrjt-$npm install jade --save-dev

Now, if you want to install or update all the dependencies of a NodeJS project, go to the project folder in the terminal and use the below commands. All the dependencies mentioned in the package.json will be installed with this.

#Install all the dependencies of the project
MyNodePrjt-$npm install

#Update all the dependencies of the project
MyNodePrjt-$npm update

Lastly, to get more info you can do an npm help in the terminal. All the above commands listed are most frequently used ones. To get info on available npm packages check npmjs.