What is Node Package Manager?

NPM is a component of Node.js, so before you can use it you must first install Node.js. You can find installers for both Mac and Windows at nodejs.org. Once you have Node.js installed, using NPM is incredibly easy and is done from the Command Line Interface (CLI). Start by ensuring you have the latest version of NPM installed, as it is updated more often than Node.js itself:

$ npm install -g npm

When using NPM, the -g option will apply your changes to your global environment. In this case, you want your version of NPM to apply globally. As stated previously, NPM can be used to manage packages both globally and within isolated environments. In the following, we want essential development tools to be applied globally so that you can use them in multiple projects on the same system.

For any project you develop, you will keep a local package.json file to manage your Node.js dependencies. This file should be stored at the root of your project directory and it will only pertain to that isolated environment. This allows you to have multiple Node.js projects with different dependency chains on the same system.

When beginning a new project, you can automate the creation of the package.json file from the command line:

$ npm init

Running npm init will take you through a series of JSON property names to define through command line prompts, including your app's name, version number, description, and more. The name and version properties are required, and your Node.js package will not install without them defined. Several of the properties will have a default value given within parentheses in the prompt so that you may simply hit Enter to continue. Other properties will simply allow you to hit Enter with a blank entry and will not be saved to the package.json file, or will be saved with a blank value:

name: (my-app)
version: (1.0.0)
description:
entry point: (index.js)

The entry point prompt will be defined as the main property in package.json and is not necessary unless you are developing a Node.js application. In our case, we can forgo this field. The npm init command may in fact force you to save the main property, so you will have to edit package.json afterward to remove it; however, that field will have no effect on your web app.

You may also choose to create the package.json file manually using a text editor, if you know the appropriate structure to employ. Whichever method you choose, your initial version of the package.json file should look similar to the following example:

{ 
  "name": "my-app", 
  "version": "1.0.0", 
  "author": "Philip Klauzinski", 
  "license": "MIT", 
  "description": "My JavaScript single page application." 
} 

If you want your project to be private and want to ensure that it does not accidently get published to the NPM registry, you may want to add the private property to your package.json file, and set it to true. Additionally, you may remove some properties that only apply to a registered package:

{ 
  "name": "my-app", 
  "author": "Philip Klauzinski", 
  "description": "My JavaScript single page application.", 
  "private": true 
} 

Once you have your package.json file set up the way you like it, you can begin installing Node.js packages locally for your app. This is where the importance of dependencies begins to surface.

$ npm install browserify --save-dev

{ 
  "name": "my-app", 
  "version": "1.0.0", 
  "author": "Philip Klauzinski", 
  "license": "MIT", 
  "devDependencies": { 
    "browserify": "^12.0.1" 
  } 
} 
 

$ npm update --save-dev

$ npm update -D

$ npm update -g