What is the difference between 'npm install' and 'npm install --save'?

npm (Node Package Manager) is a package manager and distribution tool for Node.js, used to manage dependencies in projects.

Basic Differences

• npm install <package_name>: This command installs the specified package into the node_modules directory without modifying the package.json file. If the dependency is already listed in package.json with a specified version, it will be installed using that version; otherwise, the latest version is installed.
• npm install <package_name> --save: This command not only installs the package but also adds it as a dependency to the package.json file. Consequently, when others clone your project and run npm install, this package will be installed automatically.

Usage Scenarios and Importance

• Development Dependencies vs. Production Dependencies: In practical development, libraries required for the application to run are typically listed as production dependencies, while tools for testing and building projects are designated as development dependencies. Using the --save flag adds dependencies to the dependencies section, which is the default behavior. To add a dependency as a development dependency, use --save-dev.
• Project Maintainability and Collaboration: Explicitly recording dependencies in package.json ensures that team members or deployers can consistently install identical dependency versions, thereby avoiding issues caused by version discrepancies.

Example

Suppose you are developing a Node.js web application and need to install the Express framework. You would run:

bash
npm install express --save

This adds Express to the dependencies section of your package.json, ensuring that other developers can install the same package when they clone your project using npm install.

Summary

In short, the key difference between npm install <package_name> and npm install <package_name> --save is that the latter modifies the package.json file to include the installed package in the project dependencies, which is critical for dependency management. Starting from npm 5.x, --save became the default behavior, so with newer npm versions, even running npm install <package_name> alone will add dependencies to package.json.