Node.js – NPM

Node.js – NPM

Node Package Manager (NPM) provides two main functionalities −

  • Online repositories for node.js packages/modules which are searchable on
  • Command line utility to install Node.js packages, do version management and dependency management of Node.js packages.
    >npm --version

    Installing Modules using NPM

    There is a simple syntax to install any Node.js module −

    $ npm install <Module Name>

    For example, following is the command to install a famous Node.js web framework module called express −

    >npm install express
    added 50 packages, and audited 51 packages in 5s
    found 0 vulnerabilities

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

    var express = require('express');

    Global vs Local Installation

    By default, NPM installs any dependency in the local mode. Here local mode refers to the package installation in node_modules directory lying in the folder where Node application is present. Locally deployed packages are accessible via require() method. For example, when we installed express module, it created node_modules directory in the current directory where it installed the express module.

    $ ls -l
    total 0
    drwxr-xr-x 3 root node_modules

    Alternatively, you can use npm ls command to list down all the locally installed modules.
    Globally installed packages/dependencies are stored in system directory. Such dependencies can be used in CLI (Command Line Interface) function of any node.js but cannot be imported using require() in Node application directly. Now let's try installing the express module using global installation.

    >npm install express -g
    changed 50 packages, and audited 51 packages in 4s
    found 0 vulnerabilities

    This will produce a similar result but the module will be installed globally. Here, the first line shows the module version and the location where it is getting installed.

    └── express@4.17.1 /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)

    You can use the following command 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 present in node_modules/express/

    "name": "express",
    "description": "Fast, unopinionated, minimalist web framework",
    "version": "4.17.1",
    "author": "TJ Holowaychuk ",
    "contributors": [
    "Aaron Heckmann ",
    "Ciaran Jessup ",
    "Douglas Christopher Wilson ",
    "Guillermo Rauch ",
    "Jonathan Ong ",
    "Roman Shtylman ",
    "Young Jae Sim "
    "license": "MIT",
    "repository": "expressjs/express",
    "homepage": "",
    "keywords": [
    "dependencies": {
    "accepts": "~1.3.7",
    "array-flatten": "1.1.1",
    "body-parser": "1.19.0",
    "content-disposition": "0.5.3",
    "content-type": "~1.0.4",
    "cookie": "0.4.0",
    "cookie-signature": "1.0.6",
    "debug": "2.6.9",
    "depd": "~1.1.2",
    "encodeurl": "~1.0.2",
    "escape-html": "~1.0.3",
    "etag": "~1.8.1",
    "finalhandler": "~1.1.2",
    "fresh": "0.5.2",
    "merge-descriptors": "1.0.1",
    "methods": "~1.1.2",
    "on-finished": "~2.3.0",
    "parseurl": "~1.3.3",
    "path-to-regexp": "0.1.7",
    "proxy-addr": "~2.0.5",
    "qs": "6.7.0",
    "range-parser": "~1.2.1",
    "safe-buffer": "5.1.2",
    "send": "0.17.1",
    "serve-static": "1.14.1",
    "setprototypeof": "1.1.1",
    "statuses": "~1.5.0",
    "type-is": "~1.6.18",
    "utils-merge": "1.0.1",
    "vary": "~1.1.2"
    "devDependencies": {
    "after": "0.8.2",
    "connect-redis": "3.4.1",
    "cookie-parser": "~1.4.4",
    "cookie-session": "1.3.3",
    "ejs": "2.6.1",
    "eslint": "2.13.1",
    "express-session": "1.16.1",
    "hbs": "4.0.4",
    "istanbul": "0.4.5",
    "marked": "0.6.2",
    "method-override": "3.0.0",
    "mocha": "5.2.0",
    "morgan": "1.9.1",
    "multiparty": "4.2.1",
    "pbkdf2-password": "1.2.1",
    "should": "13.2.3",
    "supertest": "3.3.0",
    "vhost": "~3.0.2"
    "engines": {
    "node": ">= 0.10.0"
    "files": [
    "scripts": {
    "lint": "eslint .",
    "test": "mocha --require test/support/env --reporter spec --bail --check-leaks test/ test/acceptance/",
    "test-ci": "istanbul cover node_modules/mocha/bin/_mocha --report lcovonly -- --require test/support/env --reporter spec --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/"

    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

    Use the following command to uninstall a Node.js module.

    $ npm uninstall express

    Once NPM uninstalls the package, you can verify it by looking at the content of /node_modules/ directory or type the following command −

    $ npm ls

    Updating a Module

    Update package.json and 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's generate package.json using NPM, which will generate the basic 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  --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: (demo)

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

    $ npm adduser
    Username: prutor
    Email: (this IS public)

    It is time now to publish your module −

    $ npm publish

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

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