Node.js | NPM (Node Package Manager)

Hello folks! welcome back to a new edition of our tutorial on Node.js. In this section of our tutorial on Node.js, we will be studying about Node.js NPM.

Node Package Manager provides two main functionalities -

• Online repositories for Node.js packages and modules which are searchable on search.node.js.org

• Command line utility to install Node.js packages, do version management and dependency managements of Node.js packages.

NPM comes packed with node.js installable after version 0.6.3. To verify the same, open console and type in the following command and see the result -

$ npm --version
8.3.1

If you are running an old version of NPM, it is very simple to update it to latest version. Just use the following command from root -

$ sudo npm install npm -g
/usr/bin/npm -> /usr/lib/node_modules/npm/bin/npm-cli.js
npm@2.7.1 /usr/lib/node_modules/npm

Installing Modules via NPM

There is a simple syntax for Installing any Node.js module -

$ npm install <Module Name>

Example

Following below is the command to install a well known Node.js web framework module called express -

$ npm install express

Now, you can use this module in your js file as follows -

var express = require('express');

READ: Node.js | REPL Terminal

Global vs Local Installation

By default, NPM installs any dependency in the local mode. Here, a local mode refers to the package Installation in the node_module directory lying inside the folder where Node application is present. The locally deployed packages are accessable through require() method. For example, when we installed the express module, it created a node_modules directory in the current directory where the express module was installed.

$ ls -l
total 0
drwxr-xr-x 3 root root 20 Mar 14 02:23 node_modules

Alternatively, you can use npm ls command to list down all locally installed modules.

Globally installed dependencies are stored in the system directory. Such dependencies can be used in the Command Line Interface function of any Node but can't be imported using require() method in Node application directly.

Example

Let us try installing the express module via global Installation.

$ npm install express -g

This is going to produce a similar result but the module will be installed globally. Here, the first line shows the module version and the location of its Installation.

express@4.12.2 /usr/lib/node_modules/express
├── merge-descriptors@1.0.0
├── utils-merge@1.0.0
├── cookie-signature@1.0.6
├── methods@1.1.1
├── fresh@0.2.4
├── cookie@0.1.2
├── escape-html@1.0.1
├── range-parser@1.0.2
├── content-type@1.0.1
├── finalhandler@0.3.3
├── vary@1.0.0
├── parseurl@1.3.0
├── content-disposition@0.5.0
├── path-to-regexp@0.1.3
├── depd@1.0.0
├── qs@2.3.3
├── on-finished@2.2.0 (ee-first@1.1.0)
├── etag@1.5.1 (crc@3.2.1)
├── debug@2.1.3 (ms@0.7.0)
├── proxy-addr@1.0.7 (forwarded@0.1.0, ipaddr.js@0.1.9)
├── send@0.12.1 (destroy@1.0.3, ms@0.7.0, mime@1.3.4)
├── serve-static@1.9.2 (send@0.12.2)
├── accepts@1.2.5 (negotiator@0.5.1, mime-types@2.0.10)
└── type-is@1.6.1 (media-typer@0.3.0, mime-types@2.0.10)

Following command can be used to check all the modules installed globally.

$ npm ls -g

Using package.json

package.json is present in the root directory of any node application/module and is used to define the properties of a package. Let's open package.json of express package that is present in node_modules/express/ -

{
   "name": "express",
      "description": "Fast, unopinionated, minimalist web framework",
      "version": "4.11.2",
      "author": {
      
         "name": "TJ Holowaychuk",
         "email": "tj@vision-media.ca"
      },
   
   "contributors": [{
      "name": "Aaron Heckmann",
      "email": "aaron.heckmann+github@gmail.com"
   }, 
   
   {
      "name": "Ciaran Jessup",
      "email": "ciaranj@gmail.com"
   },
   
   {
      "name": "Douglas Christopher Wilson",
      "email": "doug@somethingdoug.com"
   },
   
   {
      "name": "Guillermo Rauch",
      "email": "rauchg@gmail.com"
   },
   
   {
      "name": "Jonathan Ong",
      "email": "me@jongleberry.com"
   },
   
   {
      "name": "Roman Shtylman",
      "email": "shtylman+expressjs@gmail.com"
   },
   
   {
      "name": "Young Jae Sim",
      "email": "hanul@hanul.me"
   } ],
   
   "license": "MIT", "repository": {
      "type": "git",
      "url": "https://github.com/strongloop/express"
   },
   
   "homepage": "https://expressjs.com/", "keywords": [
      "express",
      "framework",
      "sinatra",
      "web",
      "rest",
      "restful",
      "router",
      "app",
      "api"
   ],
   
   "dependencies": {
      "accepts": "~1.2.3",
      "content-disposition": "0.5.0",
      "cookie-signature": "1.0.5",
      "debug": "~2.1.1",
      "depd": "~1.0.0",
      "escape-html": "1.0.1",
      "etag": "~1.5.1",
      "finalhandler": "0.3.3",
      "fresh": "0.2.4",
      "media-typer": "0.3.0",
      "methods": "~1.1.1",
      "on-finished": "~2.2.0",
      "parseurl": "~1.3.0",
      "path-to-regexp": "0.1.3",
      "proxy-addr": "~1.0.6",
      "qs": "2.3.3",
      "range-parser": "~1.0.2",
      "send": "0.11.1",
      "serve-static": "~1.8.1",
      "type-is": "~1.5.6",
      "vary": "~1.0.0",
      "cookie": "0.1.2",
      "merge-descriptors": "0.0.2",
      "utils-merge": "1.0.0"
   },
   
   "devDependencies": {
      "after": "0.8.1",
      "ejs": "2.1.4",
      "istanbul": "0.3.5",
      "marked": "0.3.3",
      "mocha": "~2.1.0",
      "should": "~4.6.2",
      "supertest": "~0.15.0",
      "hjs": "~0.0.6",
      "body-parser": "~1.11.0",
      "connect-redis": "~2.2.0",
      "cookie-parser": "~1.3.3",
      "express-session": "~1.10.2",
      "jade": "~1.9.1",
      "method-override": "~2.3.1",
      "morgan": "~1.5.1",
      "multiparty": "~4.1.1",
      "vhost": "~3.0.0"
   },
   
   "engines": {
      "node": ">= 0.10.0"
   },
   
   "files": [
      "LICENSE",
      "History.md",
      "Readme.md",
      "index.js",
      "lib/"
   ],
   
   "scripts": {
      "test": "mocha --require test/support/env 
         --reporter spec --bail --check-leaks test/ test/acceptance/",
      "test-cov": "istanbul cover node_modules/mocha/bin/_mocha 
         -- --require test/support/env --reporter dot --check-leaks test/ test/acceptance/",
      "test-tap": "mocha --require test/support/env 
         --reporter tap --check-leaks test/ test/acceptance/",
      "test-travis": "istanbul cover node_modules/mocha/bin/_mocha 
         --report lcovonly -- --require test/support/env 
         --reporter spec --check-leaks test/ test/acceptance/"
   },
   
   "gitHead": "63ab25579bda70b4927a179b580a9c580b6c7ada",
   "bugs": {
      "url": "https://github.com/strongloop/express/issues"
   },
   
   "_id": "express@4.11.2",
   "_shasum": "8df3d5a9ac848585f00a0777601823faecd3b148",
   "_from": "express@*",
   "_npmVersion": "1.4.28",
   "_npmUser": {
      "name": "dougwilson",
      "email": "doug@somethingdoug.com"
   },
   
   "maintainers": [{
      "name": "tjholowaychuk",
      "email": "tj@vision-media.ca"
   },
   
   {
      "name": "jongleberry",
      "email": "jonathanrichardong@gmail.com"
   },
   
   {
      "name": "shtylman",
      "email": "shtylman@gmail.com"
   },
   
   {
      "name": "dougwilson",
      "email": "doug@somethingdoug.com"
   },
   
   {
      "name": "aredridel",
      "email": "aredridel@nbtsc.org"
   },
   
   {
      "name": "strongloop",
      "email": "callback@strongloop.com"
   },
   
   {
      "name": "rfeng",
      "email": "enjoyjava@gmail.com"
   }],
   
   "dist": {
      "shasum": "8df3d5a9ac848585f00a0777601823faecd3b148",
      "tarball": "https://registry.npmjs.org/express/-/express-4.11.2.tgz"
   },
   
   "directories": {},
      "_resolved": "https://registry.npmjs.org/express/-/express-4.11.2.tgz",
      "readme": "ERROR: No README data found!"
}

READ: Node.js | Environment Setup

Attributes of Package.json

• name - name of the package.

• version - version of the package.

• description - description of the package.

• homepage - homepage of the package.

• author - author of the package.

• contributors - name of the contributors to the package.

• dependencies - list of dependencies. NPM automatically installs all the dependencies mentioned here in the node_module folder of the package.

• repository - repository type and URL of the package.

• main - entry point of the package.

• keywords - keywords.

Uninstalling a Module

The following command below can be used to uninstall a Node.js module -

$ npm uninstall express

Once NPM uninstalls the package, you can easily verify it by going through the content of /node_modules/ directory or can type the following command -

$ npm ls

Updating a Module

Update package.json and then change the version of the dependency to be updated and run the following command -

$ npm update express

Search a Module

Search a package name using NPM.

$ npm search express

Create a Module

Creating a module requires package.json to be generated. Let us generate package.json using NPM, which will generate the primary skeleton of the package.json.

$ npm init
This utility will walk you through creating a package.json file.
It only covers the most common items, and tries to guess sane defaults.

See 'npm help json' for definitive documentation on these fields
and exactly what they do.

Use 'npm install <pkg> --save' afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
name: (webmaster)

You need to provide all required information about your module. You can take help from above mentioned package.json file in order to understand the meanings of the different information demanded. Once package.json is generated, use the following command to register yourself with an NPM repository site using a valid email address.

$ npm adduser
Username: mcmohd
Password:
Email: (this IS public) mcmohd@gmail.com

It is time to now publish your module.

$ npm publish

If everything is fine with your module, then it will be published in the repository and it will be accessible to install making use of NPM like any other Node.js module.

READ: Node.js | Introduction

Alright guys! This is where we are going to be rounding up for this tutorial. In our next tutorial, we will be studying about Node.js Callbacks Concept.

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Thanks for reading and bye for now.