Adding and Removing Packages

When you find a cool tool on the NPM website, you need to "install" it to use it in your code.

There are two main ways to install packages, depending on when you need them.

1. Production Dependencies (--save)

These are the "Main Ingredients." Your website needs these to function for the user. If you are building a calculator, the math library you use is a production dependency.

The Command:

npm install lodash

• What happens? NPM downloads the code into node_modules and adds it to the "dependencies" section of your package.json.
• Shortcut: You can just type npm i lodash.

2. Dev Dependencies (--save-dev)

These are the "Kitchen Tools." You need a knife and a pan to cook the meal, but the customer doesn't eat the knife!

"DevDeps" are tools you only use while you are coding (like a tool that auto-refreshes your browser or a code-cleaner).

The Command:

npm install nodemon --save-dev

• Shortcut: You can use -D as a shortcut: npm i nodemon -D.
• Look inside: These will appear in a special "devDependencies" section in your package.json.

What is this package-lock.json file?

The moment you install your first package, a new, scary-looking file called package-lock.json will appear.

Don't delete it! Think of it as a Security Seal. While package.json says "I need a math library," the package-lock.json says "I need exactly version 4.17.21 of the math library with this specific security ID."

It ensures that if 10 people are working on the same project at CodeHarborHub, everyone has the exact same version of the code.

Removing a Package

If you decide you don't like a tool, don't just delete the folder manually. Use the "clean-up" command:

npm uninstall lodash

This safely removes the code from node_modules and deletes the line from your package.json recipe.

Summary Comparison

Type	Command	Where it goes	Purpose
Dependency	npm i <name>	"dependencies"	Needed for the website to run.
DevDependency	npm i <name> -D	"devDependencies"	Only needed by the developer.

Summary Checklist

• I can install a package using npm i.
• I understand that -D is for tools only I (the developer) use.
• I know that package-lock.json is a security lock for versions.
• I can use npm uninstall to keep my project clean.