What is Node.js NPM ?
NPM stands for Node Package Manager. NPM provides two main functionalities −
Online repositories for node.js packages/modules which are searchable on search.nodejs.org
Command line utility to install Node.js packages, do version management and dependency management of Node.js packages.
NPM comes bundled with Node.js installables after v0.6.3 version. To verify the same, open console and type the following command and you will see the result:
$ npm --version 2.7.1
If you are running an old version of NPM then it is quite easy to update it to the latest version. You just have to 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 using NPM
There is a simple syntax to install any Node.js module:
$ npm install <Module Name>
For example, the command to install a famous Node.js web framework module called express is:
$ npm install express
Now you can use this module in your js file as:
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 root 20 Mar 17 02:23 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
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@4.12.2 /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)
You can also 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/
{
"_from": "express@^4.17.1",
"_id": "express@4.17.1",
"_inBundle": false,
"_integrity": "sha512-mHJ9O79RqluphRrcw2X/GTh3k9tVv8YcoyY4Kkh4WDMUYKRZUq0h1o0w2rrrxBqM7VoeUVqgb27xlEMXTnYt4g==",
"_location": "/express",
"_phantomChildren": {},
"_requested": {
"type": "range",
"registry": true,
"raw": "express@^4.17.1",
"name": "express",
"escapedName": "express",
"rawSpec": "^4.17.1",
"saveSpec": null,
"fetchSpec": "^4.17.1"
},
"_requiredBy": [
"#USER",
"/"
],
"_resolved": "https://registry.npmjs.org/express/-/express-4.17.1.tgz",
"_shasum": "4491fc38605cf51f8629d39c2b5d026f98a4c134",
"_spec": "express@^4.17.1",
"_where": "C:\\Users\\Sharad\\register",
"author": {
"name": "TJ Holowaychuk",
"email": "tj@vision-media.ca"
},
"bugs": {
"url": "https://github.com/expressjs/express/issues"
},
"bundleDependencies": false,
"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"
}
],
"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"
},
"deprecated": false,
"description": "Fast, unopinionated, minimalist web framework",
"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": [
"LICENSE",
"History.md",
"Readme.md",
"index.js",
"lib/"
],
"homepage": "http://expressjs.com/",
"keywords": [
"express",
"framework",
"sinatra",
"web",
"rest",
"restful",
"router",
"app",
"api"
],
"license": "MIT",
"name": "express",
"repository": {
"type": "git",
"url": "git+https://github.com/expressjs/express.git"
},
"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/"
},
"version": "4.17.1"
}
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
To uninstall a module in Node.js we have to use the following command:
$ npm uninstall express
Once NPM uninstalls the package, you can verify it by looking at the content of /node_modules/ directory or you can simply type the following command:
$ npm ls
Updating a Module
To update package.json and change the version of the dependency you have to run the following command:
$ npm update express
Search a Module
To 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 Press ^C at any time to quit. name: (webmaster)
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: mcmohd Password: Email: (this IS public) mcmohd@gmail.com
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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