Node.js

• Ideal for building real-time applications, APIs, and microservices.
• Written in C++
• Download NodeJs on your OS
  • The installer will install npm package manager by default
  • Recommended to install Node Version Manager to easily change between node versions.
• npm is a package manager that allows install tons of JS libraries from community.

1. Create a Project

• Create a folder
• In this directory, execute

npm init

• A package.json is created
• Every Node project has a package.json providing information such as project's name, author, version, and dependencies.

2. Install dependencies

• Install all the libraries with their specific version that package.json specifies

npm i

3. Run Project ✅

• If you want to run your project, already set up. We can use the next command:

node file-name.js

Nodemon (Live Server) 💨

• Another alternative to run our projects, Nodemon
• Nodemon is like Live Server but in Node.js
• Normally, to see our changes in a Nodejs project, we would need to shut down server and start it again
• Nodemon does this automatically, save our lifes!

Install Nodemon:

npm i nodemon

Once installed, add these lines to the "package.json" $\rightarrow$ "scripts"

...
"scripts" : {
  //"dev": "nodemon index.js",
  "start": "nodemon index.js"
},
...

Note: Create index.js/other_name.js. Here must have your app.listen(PORT)

Now, we can RUN our project with Nodemon

npm run start

To fix this:

• Create in root directory: nodemon.json
• Add a JSON

{
  "ext": "js,json,ejs,hbs, <otherFileExtensions>"
}

• Restart server to take effect: Ctrl+C then npm run start

Setting PORT 🔨

We usually run our project on a server. For example, Live Server uses PORT 3000 so we can view our project on localhost:3000.

In NodeJS, we must set up manually. In index.js:

const express = require('express')
const app = express()
 
const PORT = 3000 // Can use any port number
app.listen(PORT, () => console.log(`Server: http://localhost:${PORT}`))

Node Asyn 🆚 Sync

Node supports both synchronous and asynchronous

• Synchronous Programming
  • Code that performs one task after another, waiting for one to complete before starting another
• Asynchronous Programming
  • We don't wait for the code to finish, it's async

Event Loop 🔄

Responsible for managing tasks in the queues, and decides which task execute next in the Call Stack.

The Event Loop does the following process:

• Takes a MacroTask from the queue and execute
• Next, takes a microTask from queue and execute
  • keeps executing microTasks until there is none
  • No MacroTask is selected until microTasks are done
• Once microtask are done, next a new MacroTask takes in to be process