Day 7 : All about NPM

NPM stands for node package manager. It is a package manager for node.js applications. It helps you to install , update, remove and publish packages. Node.js package ecosystem is the world's largest ecosystem of open source online libraries. We never have to write a already existing code again which reduces the efforts of the programmers upto a large extent and they can focus on solving the unsolved problems instead of rewriting the same code again and again.

Installing npm automatically : NPM is installed automatically by downloading node.js. You can donwload node.js here .

Installing npm manually : We can also install npm manually. You can get the file from the link given below :
https://registry.npmjs.org/npm/-/npm-{version}.tgz
All you have to do is change the version number just like the example given below : https://registry.npmjs.org/npm/-/npm-5.4.2.tgz
Note : Not for noobs.

NPM updates comes more frequently as compared to node.js and we can't download node.js again and again just to update npm. So we have to make sure that we are using the latest version of npm . We can update a npm using the following command :

								
>npm install npm@latest -g
								
							

								
>npm -v
								
							

1. package.json is a way to manage the locally installed packages.
2. package.json serves as documentation on which our project depends.
3. It is kind of a directory which keeps track of all the dependencies our project is using.
4. It allows us to specify the versions of packages our project is using. This is achieved using semantic versioning rules.

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

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

Use `npm install ` afterwards to install a package and
save it as a dependency in the package.json file.

Press ^C at any time to quit.
package name: (nodejsera)
version: (1.0.0)
description:
entry point: (arrays.js)
test command:
git repository:
keywords:
author: @rajatgarian
license: (ISC)
About to write to \package.json:

{
  "name": "scripts",
  "version": "1.0.0",
  "description": "",
  "main": "arrays.js",
  "dependencies": {
    "body-parser": "^1.17.2",
    "express": "^4.15.4",
    "ejs": "^2.5.7",
    "express-fileupload": "^0.1.4",
    "nodemailer": "^4.1.0",
    "natural": "^0.5.4",
    "prettyjson": "^1.2.1"
  },
  "devDependencies": {},
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "@rajatgarian",
  "license": "ISC"
}


Is this ok? (yes) yes
					
				

								
npm init --yes				
								
				

If we are having a package.json file in our project , then we can install all our dependencies using just npm install command. Example for the same is given below ::

											
>npm install
											
										

In npm , there are 2 ways in which we can install our packages :

1. Locally (Local installation ) : We install packages locally when we need to require them in our application for example express, gannit , etc. The syntax for downloading a package locally is : npm install < package_name > .
   Example for the same is given below ::
   

   											
   >npm install gannit
   											
   										

   
   This command will create a folder/directory in your pwd ( present working directory ) with the name of node_modules ( only if it is not yet created ) and download the package in that directory.
   Test : We can test whether the command npm install worked or not by manually checking whether the directory with the name of node_modules exists or not . And secondly if node_modules directory exists , does it contain a directory for the package we installed.
2. Globally (Global installation) : We install packages globally when we want to use it as a command line tool or run it in the background for example forever, grunt-cli, etc. The syntax for global download of packages is : npm install -g < package_name > .
   Example is given below :
   

   											
   >npm install -g forever
   											
   										

   
   And that's it, the downloaded package is ready to use.

1. You Know the exact version : If you know the exact version of the npm package you want to install , then it can be downloaded using the package_name with @ character. The Syntax is npm install package_name@version . The snippet is given below :
   

   											
   >npm install express@4.15.1
   											
   										

   
   
2. You don't Know the exact version : If you don't know the exact version of the npm package you want to install , then it can be downloaded using the semantic range npm provides. Suppose you want to install the latest version of the 4th major release say , 4.1.15 then you can download it in the following way : The Syntax is npm install package_name@^major_version.0.0 . The snippet is given below :
   

   											
   >npm install express@^4.0.0
   											
   										

   
   

1. Updating local packages : We should keep our packages updated in order to keep track of the changes that have been made to the code upstream of the packages so that we can mould our code as per the latest version. The syntax for Updating local packages is : npm update .
   Example is given below :
   

   											
   >npm update
   											
   										

   
   Note : Run this command in the same folder as package.json file.
   Test : We can test whether the command npm install worked or not by running the command npm outdated command. If there is no output on the console , then it means all the packages are updated.
   

   											
   >npm outdated
   											
   										

   
   
2. Updating global packages : The Syntax for updating global packages is npm install -g < package_name > The snippet is given below :
   

   											
   >npm install -g forever
   											
   										

   
   Finding global outdated packages : The syntax for finding outdated packages is npm outdated -g --depth=0. The snippet is given below :
   

   											
   >npm outdated -g --depth=0
   Package             Current   Wanted   Latest  Location
   @angular/cli          1.1.3    1.4.2    1.4.2	xyz
   babel                 6.5.2   6.23.0   6.23.0	xyz
   babel-cli            6.18.0   6.26.0   6.26.0	xyz
   nodemon              1.11.0   1.12.1   1.12.1	xyz
   sails                0.11.0  0.12.13  0.12.13	xyz
   webpack              1.13.3    3.6.0    3.6.0	xyz
   webpack-dev-server   1.16.2    2.8.2    2.8.2	xyz											
   											
   										

   
   The output of the above command is explained in detail below :
   • package : Contains the name of the package.
   • current : The current version of the package installed.
   • Wanted : It specifies the maximum version of the package as mentioned in package.json that satisfies semver . It shows the currently installed version of the package if we have no semver i.e. we are running npm outdated global -g , or the package is not included in package.json.
   • Latest : It specifies the latest available version of the package in the registry.
   • Location : Specifies the location of the installed package.
   
   Update all outdated packages (Global) : We can update all the outdated global packages by using just one command. The snippet is given below :
   

   											
   npm update -g										
   											
   										

   
   

In npm , there are 2 type of package installation i.e locally and globally. So , Let's see how we can remove local and global packages one by one.

1. Removing Local packages : We can remove the local packages when we do not need them further in our application. The syntax for removing a package locally is : npm uninstall < package_name > .
   Example for the same is given below ::
   

   											
   >npm uninstall gannit
   											
   										

   
   We can also remove the file from package.json by using the following command :
   

   											
   >npm uninstall --save gannit
   											
   										

   
   Moreover if we have installed the package with devDependency then we can remove it using the following command :
   

   											
   >npm uninstall --save-dev gannit
   											
   										

   
   These commands will remove the package from node_modules directory.
   Test : We can test whether the command npm uninstall worked or not by manually checking whether the package exists in the node_modules directory or not. If the package doesnot exist then it signfies that the command is executed successfully.
2. Uninstalling Global packages : We can remove the global packages the simply running npm uninstall command globally. The syntax for global download of packages is : npm uninstall -g < package_name > .
   Example is given below :
   

   											
   >npm uninstall -g forever
   											
   										

   
   And that's it, the global package is removed.

In this article , we learned about the basics of npm. How we can install packages from npm locally and globally . Updating local and global packages using npm. Removing local and global packages.