why node ?

Enables applications that can handle millions of users without blocking

-From simple webpages to largest scaled applications, to Windows/Mac desktop apps (with Electron), and hardware (embedded systems)

-Allows us to build entire applications end-to- end in one language - JavaScript.

-From client side development to full stack development

Why do we need servers ?

Servers are the behind-the-scenes of all web applications - where our client-side code/data comes from

Computer connected to the internet - a permanent store of code/data, always on, ready to receive messages over the internet from users requesting code/data and send it back

— How’s this computer know what to send back?
— What languages can we use to write these instructions?

But how can we access these inbound messages as developers and send code/data back in response?

Sending the right data back requires using multiple features of the computer

-Network socket - Receive and send back messages over the internet

-Filesystem - that’s where the html/css/javascript code is stored in files

- CPU - for cryptography and optimizing hashing passwords

- Kernel - I/O management

- Our dream - be able to use JavaScript to control this computer because (1) we know JavaScript and (2) it has some really nice design decisions

How do we communicate with our computer internals ?

Each programming language (PHP, Ruby, C++, JavaScript) have different levels of ability to interact with these features directly

C++ has many features that let it directly interact with the OS directly

JavaScript does not! So it has to work with C+ + to control these computer features. What is this combination known as? ... Node.js

JS -> Node -> Computer feature (e.g. network, file system)

We had better understand JavaScript to understand Node.js then

It’s a language that does 3 things (and 1 involves a lot of help from C++)

1. Saves data and functionality (code)

2. Uses that data by running functionality (code) on it

3. Has a ton of built-in labels that trigger Node features that are built in C++ to use our computer’s internals

Using http feature of Node to set up an open socket

So let’s see JavaScript other talent - built-in labels that trigger Node features

We can set up, with a JavaScript label, a Node.js feature (and so computer internals) to wait for requests for html/css/js/tweets from our users

How? The most powerful built-in Node feature of all: http (and its associated built- in label in JS - also http conveniently)

Using http feature of Node to set up an open socket

const server = http.createServer()
server.listen(80);
function doWhenRequestCome(dataIncoming, functionsToSetOutgoingData){
    functionsToSetOutgoingData.end("Welcome to Twitter!")
}
const server = http.createServer(doOnIncoming)
server.listen(80);