npm package installation and uninstallation commands for global and local modules

NPM Basics: Installing and Uninstalling Packages

NPM (Node Package Manager) is a critical tool for managing dependencies in JavaScript projects. It allows developers to install, update, and remove packages efficiently. This guide focuses on the core commands for installing and uninstalling packages, distinguishing between global and local modules.

Installation Commands

The npm install command is the primary tool for adding packages to a project. It can be used with various flags to control behavior.

Basic Installation:
```
npm install <package-name>
```
This installs the package locally in the project’s node_modules directory. The package is recorded in the package.json file.
Saving to package.json:
```
npm install <package-name> --save
```
Adds the package to the project’s package.json file, ensuring it is included in the project’s dependencies.
Skipping package.json:
```
npm install <package-name> --no-save
```
Installs the package without updating package.json.
Installing Multiple Packages:
```
npm install package1 package2
```
Installs multiple packages simultaneously.

Uninstallation Commands

The npm uninstall command removes packages from a project. It can also be used to remove packages from global or local installations.

Removing a Package from a Project:
```
npm uninstall <package-name>
```
Deletes the package from node_modules and updates package.json.
Removing a Package from Global Installation:
```
npm uninstall -g <package-name>
```
Removes the package from the global npm registry.
Removing a Package from Local Installation:
```
npm uninstall --save <package-name>
```
Removes the package from package.json and node_modules.
Removing a Package Without Updating package.json:
```
npm uninstall --no-save <package-name>
```
Removes the package from node_modules but leaves package.json unchanged.

Global vs Local Modules

NPM packages can be installed in two modes: global or local.

Global Modules:
Packages installed with npm install -g are system-wide and available to all users. They are stored in the node_modules directory of the global npm registry.
```
npm install -g <package-name>
```
Local Modules:
Packages installed with npm install are confined to the current project. They are stored in the project’s node_modules directory and are not visible to other projects.
```
npm install <package-name>
```

Best Practices

Use --save for dependencies: Always use --save to ensure packages are included in package.json.
Avoid global installations: Global packages can be accidentally installed on multiple machines.
Check package.json: Verify installed packages with npm list to ensure consistency across environments.

By mastering these commands, developers can efficiently manage their project dependencies and avoid conflicts between global and local installations.