NPM and Dependency Management

  In the Node.js ecosystem, you'll rarely start a project from scratch without using external libraries.


  This is where NPM (Node Package Manager) comes into play, the quintessential package manager for Node.js.


  NPM is both an open-source software package registry and a command-line tool that allows you to install, manage, and share code from other developers.


Synopsis:

  NPM greatly simplifies the process of integrating third-party code into your projects and sharing your own code with the community.

  • 1. Installing packages:

    Use npm install (or `npm i` for short) followed by the package name. This downloads the package and its dependencies to your project's node_modules directory.

    To save the dependency in your package.json file (we'll see this in the next lesson), use the --save flag (which is the default behavior since NPM 5) or simplynpm install <package>.

  • 2. Production vs. development dependencies:

    Not all dependencies are necessary for your application to run in production. Some are only for development (like testing tools or linters).

    • Production dependencies (`dependencies`): Libraries your application needs to run in a production environment. Installed with `npm install <package>`.
    • Development dependencies (`devDependencies`): Libraries needed only during development and testing. Installed with `npm install <package> --save-dev`.
  • 3. Updating and uninstalling packages:

    You can update packages to their latest compatible versions or uninstall them when you no longer need them.

  • 4. npm install (without arguments):

    When you run npm install without specifying a package, NPMreads your project's `package.json` file and installs all the dependencies listed in it (both production and development). This is crucial when cloning a project from a repository.


Purpose and Usage:


  • Code Reusability: Allows easy integration of libraries and frameworks created by other developers, saving time and effort.
  • Version Management: NPM helps manage dependency versions, ensuring your project works with the correct library versions.
  • Collaboration: Facilitates collaboration on projects by allowing developers to share and manage their dependencies in a standardized way through `package.json`.
  • Fundamental Tool: It is an indispensable tool for any Node.js developer, whether you are building a REST API, a command-line application, or a web server.

  Mastering NPM is key for any Node.js project, as most advanced functionalities and frameworks rely on external libraries that are managed through this system.


Exercises


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What is the correct command to install a development dependency (only needed during development)?


JavaScript Concepts and Reference