What is the use and difference between --save and --save-dev in NPM?

NPM, or Node Package Manager, is a popular tool for managing dependencies in Node.js applications. When you use NPM to install a package, it is saved in the node_modules directory and its metadata is saved in the package.json file. This file contains information about the packages that your project depends on, including their version numbers and any other relevant metadata.
 

The npm install command is used to install packages, and it provides several options that can be used to customize how packages are installed. Two of the most commonly used options are --save and --save-dev. These options specify whether a package should be installed as a production dependency or as a development dependency. In this article, we'll explain the difference between these two options and provide examples of when each should be used.

What is a Production Dependency?

A production dependency is a package that is required for your application to run correctly. These packages are installed when your application is deployed and are used to provide core functionality. For example, if you are building a web application using Express.js, you will need to install Express.js as a production dependency:

<code> npm install --save express</code>
 

This command installs Express.js and adds it to the dependencies section of the package.json file. When you deploy your application, NPM will install all of the packages listed in the dependencies section.

 

What is a Development Dependency?

A development dependency is a package that is only required during development. These packages are not necessary for your application to run correctly, but they may be required for testing, building, or debugging your application. For example, if you are using Mocha as your test runner, you will need to install Mocha as a development dependency:

<code>npm install --save-dev mocha</code>

 

This command installs Mocha and adds it to the devDependencies section of the package.json file. When you run your tests, NPM will install all of the packages listed in the devDependencies section.

 

When to Use --save vs --save-dev

Knowing when to use --save vs --save-dev is important for keeping your project organized and ensuring that your dependencies are managed correctly. Here are some general guidelines:

Use --save for Production Dependencies

Use --save when installing packages that are required for your application to run correctly. These packages should be production dependencies and should be installed in the dependencies section of the package.json file.

 

For example, if you are building a web application using Express.js, you should use --save to install Express.js:

<code>npm install --save express</code>

 

Use --save-dev for Development Dependencies

Use --save-dev when installing packages that are only required during development, such as test runners or build tools. These packages should be installed in the devDependencies section of the package.json file.

 

For example, if you are using Mocha as your test runner, you should use --save-dev to install Mocha:

<code>npm install --save-dev mocha</code>
 

Benefits of Using --save and --save-dev

Using --save and --save-dev options provide several benefits:

 

Better Dependency Management

Using --save and --save-dev options allows developers to manage project dependencies more efficiently. By separating production and development dependencies, it is easier to keep track of which packages are required for the application to run and which packages are only needed during development.