NPM

Key Features of NPM (Node Package Manager)

1. A Node.js package/module repository searchable on NPMSearch

2. A command-line utility for installing Node.js packages and managing versions/compatibility

Check npm installation

$ npm --version
6.13.4

npm version update

sudo npm install npm -g

Installing Modules using NPM

Syntax to install any Node.js module

npm install <Module Name>

Install a famous Node.js web framework module called express

npm install express

Now you can use this module in your js file as following

var express = require('express');

Global vs Local Installation

By default, npm installs modules in local mode

• Local mode

  : Means installing the package in the node_modules directory within the directory where the command was executed

• Global mode

  : Means installing in the System directory

Install express in global mode

$ sudo npm install express -g
/usr/lib
└─┬ express@4.13.4
 ├─┬ accepts@1.2.13
 │ ├─┬ mime-types@2.1.9
 │ │ └── mime-db@1.21.0
 │ └── negotiator@0.5.3
 .... truncated for brevity....
 │ └── statuses@1.2.1
 ├── utils-merge@1.0.0
 └── vary@1.0.1

• You can see that the module is installed in /usr/lib/node_modules, not in the current path

• Since it saves to the system, you need to prefix with sudo if you are not the root user!

• When installed in Global mode, you cannot directly require it in a node application

  • but, you can use the npm link command to import the module

  npm install -g express
  cd [local path]/project
  npm link express

package.json

: Located in the path of the Node application/module and defines the properties of the package

package.json generated when creating a project with express

{
  "name": "myapp",
  "version": "0.0.0",
  "private": true,
  "scripts": {
    "start": "node ./bin/www"
  },
  "dependencies": {
    "body-parser": "~1.13.2",
    "cookie-parser": "~1.3.5",
    "debug": "~2.2.0",
    "express": "~4.13.1",
    "jade": "~1.11.0",
    "morgan": "~1.6.1",
    "serve-favicon": "~2.3.0"
  }
}

• package.json contains information about the modules and module versions that the project depends on

Uninstalling a Module

npm uninstall express

Updating a Module

npm update express

Search a Module

npm search express

• This command consumes a lot of memory the first time it is used

  • If you are using a Cloud IDE or your server has about 1G of RAM, it will take a very long time or cause errors

  • In that case, search on NPMSearch!