Initializing a Node.js app that utilizesnpmis a relatively straightforward process. To initialize a Node.js app, we open up a terminal and enter the command:

npm init

This will result in a series of prompts asking us forinformation about our project, including our project’s name, version number, and description. Once the prompts have been completed, apackage.jsonfile will be generated with the information listed inJSONformat:

{  "name": "my-project",  "version": "1.0.0",  "description": "a basic project",  "main": "index.js",  "scripts": {    "test": "echo \"Error: no test specified\" && exit 1"  },  "author": "Super Coder",  "license": "ISC",  "dependencies": {    "express": "^4.18.2"  },}
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{  "name": "my-project",  "version": "1.0.0",  "description": "a basic project",  "main": "index.js",  "scripts": {    "test": "echo \"Error: no test specified\" && exit 1"  },  "author": "Super Coder",  "license": "ISC",  "dependencies": {    "express": "^4.18.2"  },}

Quick tip: If you’re looking to get initialized quickly, you can add the flag-yto the end of the initialization command to skip the prompts like so:npm init -y.

Direct your attention to the"dependencies"dictionary in the file above. This section lists all of the project’s dependencies alongside their version numbers. Importantly, as you install new dependencies usingnpm, this file will be automatically updated to maintain the most up-to-date picture of the packages used in the application. As you can see, this project already has the popular routing packageexpresslisted as a dependency.

How to install a package using npm

There are over 1 million packages in the npm registry created by developers just like you, and you can explore the collection on theofficial npm website.

Another popular Node.js package isnodemon, a tool used to automatically restart a program when a file changes, alleviating the need to do so manually each time you save a file. You can enter “nodemon” in the search bar of the npm website, or just Google “nodemon npm” to get to theofficial package page.

Each package’snpmpage includes information on using the package, stats about the package, and a link to theGitHubrepository. At the top of the right sidebar, you’ll see the install command:

npm website showing install command

In this case:

npm i nodemon

Note:iis actually an alias forinstall, and eithernpm iornpm installcan be used when installing a package.

Thenpm i <package name>command installs a packagelocallyin a folder callednode_modules/which is created in the project directory that you ran the command from. Additionally, the newly installed package will be added to thepackage.jsonfile:

{  "name": "my-project",  "version": "1.0.0",  "description": "a basic project",  "main": "index.js",  "scripts": {    "test": "echo \"Error: no test specified\" && exit 1"  },  "author": "Super Coder",  "license": "ISC",  "dependencies": {    "express": "^4.18.2",    "nodemon": "^3.1.10"  }}
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{  "name": "my-project",  "version": "1.0.0",  "description": "a basic project",  "main": "index.js",  "scripts": {    "test": "echo \"Error: no test specified\" && exit 1"  },  "author": "Super Coder",  "license": "ISC",  "dependencies": {    "express": "^4.18.2",    "nodemon": "^3.1.10"  }}

Different ways to install npm packages

Generally, most npm packages should be installed locally — this way, among other reasons, each project can control which specific versions of its dependencies it uses. That being said, there are a few other ways you might install packages.

How to install devDependencies in npm

While most dependencies play a direct role in the functionality of your application,development dependenciesare used for the purpose of making development easier or more efficient.

In fact, thenodemonpackage is actually better suited as a development dependency since it makes developers’ lives easier, but makes no changes to the app itself. To installnodemonas a development dependency, we can add the flag--save-dev, or its-Dalias.

npm install nodemon --save-dev

Development dependencies are listed in the"devDependencies"property ofpackage.json. This indicates that the package is being used specifically for development and will not be included in a production release of the project.

{  "name": "my-project",  "version": "1.0.0",  "description": "a basic project",  "main": "index.js",  "scripts": {    "test": "echo \"Error: no test specified\" && exit 1"  },  "author": "",  "license": "ISC",  "dependencies": {    "express": "^4.18.2"  },  "devDependencies": {    "nodemon": "^3.1.10"  }}
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{  "name": "my-project",  "version": "1.0.0",  "description": "a basic project",  "main": "index.js",  "scripts": {    "test": "echo \"Error: no test specified\" && exit 1"  },  "author": "",  "license": "ISC",  "dependencies": {    "express": "^4.18.2"  },  "devDependencies": {    "nodemon": "^3.1.10"  }}

Like local packages, development dependencies are also stored in the localnode_modules/folder.

How to install global packages in npm

Some packages can be installedglobally, meaning they are available system-wide, without the need to install them each time you create a new application. Typically, packages installed this way will be used in the command-line rather than imported into a project’s code. One such example is thehttp-serverpackagewhich allows you to spin up a zero-configuration server from anywhere in the command-line.

To install a package globally, use the-gflag with the installation command:

npm install http-server -g

http-serveris a good package to install globally since it is a general command-line utility, and its purpose is not linked to any specific functionality within an app.

Unlike local package dependencies or development dependencies, packages installed globally will not be listed in a project’spackage.json, and they will be stored ina separate, globalnode_modules/folder.

How to install all project dependencies at once

You may have noticed that, as we install third-party packages from npm, we are creating apackage.jsonfile for our own project. Doing so turns our own project into a package, just one that isn’t published in the npm registry (yet).

While you may never end up publishing your project as a public package, having thispackage.jsonfile enables you to easily collaborate with other developers. Anyone who wishes to work with you on your project can simply download your project, including thepackage.json, and run the command:

npm i

Running this command will automatically install all packages listed as dependencies or development dependencies. If you wish to leave out development dependencies, you can run the command with the--productionflag.

npm i --production

Because of this convenient command, it is recommended that you do not include your local *node_modules/folder in any repository that you use to store and share your code to avoid taking up unnecessary storage resources.

Conclusion

Congratulations on getting started with Node Package Manager andnpm! You now have a deeper understanding of packages and the various ways to usenpmto install and maintain third-party modules in our code.

Learn to manage dependencies in Node.js with Codecademy’sLearn Node.jscourse. You’ll get hands-on experience with npm, modules, and project setup.

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