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NPM(Node Package Manager)

Third party packages

To get packages which are not available in core node, go to https://www.npmjs.com/

These include things like a js utility library, a package to help in validation logic or some framework for building node websites(like express)

All of these are installed using NPM

The website contains documentation and installation instructions

Installing packages globally(nodemon)

Currently we have to restart the server file every time we make any change to our code.
Nodemon automatically restarts the server without having to restart it

Follow the installation instruction on the website

Now you can run

nodemon server

and it will do the same thing as node server except it will update the website automatically if you make changes to your server.js file

package.json file

The package file keeps track of any packages we install locally + project details and project specific scripts

To create a package.json file, run this on the terminal:

npm init

and it makes a package.json file

package.json:

{
  "name": "server",
  "version": "1.0.0",
  "description": "",
  "main": "server.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "node server.js"
  },
  "author": "",
  "license": "ISC"
}

Installing packages locally

To install lodash, we need to run this(according to the website):

$ npm i --save lodash

The --save saves it to the local dependencies for the project
Once installed, you will see package.json updated with this:

//...
"dependencies": {
    "lodash": "^4.17.21"
  }

This stores the dependencies - keeps track of all packages used in the project

When seeing documentation you may see code fragments like:

_.chunk(array, [size=1])

The _ stands for whatever we name the variable when we require it

When we installed lodash, it created a folder named node_modules which stores all the node libraries we are using for the project(you will see lodash there)

So when

const _ = require('lodash');

is run, it checks in the node_modules folder

Getting a random number using lodash:

const num = _.random(0,20);

If we want something to run exactly once, we can do:

const greet = _.once(()=>{
    console.log('hello');
});

greet(); // this is only going to run once
greet(); // this will not run again

Dependencies

Suppose someone downloads a node project and (obviously) won't download node_modules, they can get the correct node_modules since all the dependencies are noted in package.json

To re-install node_modules depending on what the dependencies are, you can just do:

npm install

This will look inside package.json and install all the dependencies