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Express(.js) Yourself ​

In the world of web development there are many things to learn, on of such things is expressjs

  • express is a fast, unopinionated, minimalistic web framework for node Its primary use is for routing, allowing you to connect pages and scripts. for instance:

Express has 5 main features:

  • routing: how an app responds to a request
  • middle ware: functions that can access request and response
  • timplating language: for generating static sites
  • extensible: using middle ware to customize the functions of the app
  • error handling: stopping an error from crashing an app

Routing ​

if your on facebook.com and click the 'profile' button you get directed to a new page, that page being something like facebook.com/profile. behind the seen express sees 'facebook.com' as '/',the 'home' page and facebook.com/profile as /profile. then in the home page the 'profile' button links to /profile and when you click it express looks through its list of routs till it finds one with the right name, then executes the function in it.

js
app.get('/'. (req, res) => {
	res.render(/*file name*/);
});

In this example, app.get tells Express to render file name when directed to '/'.

Middleware ​

Middleware are functions that have access to the request and response objects and next function witch exicutes the next middleware after it.

js
const middleware = (req, res, next) => {
// code here
	next();
}

Then you can use it in your routs

js
app.get('/', middleware, (req,res) => {
// code here
})

Or load it every time the app receives a request with `app.use(middleware);

Template language ​

A template language uses javascript to create a timplate for dinamic content that renders as html. There are many template languages like Pug and handlebars, but most use Embeded Javascript Timplate, or (EJS).

Extensible ​

With middleware expresses functionality can be extended, for example if I had middleware like this

js
const helloWorld = ((req, res, next) => {
	console.log('Hello World');
	next();
}

I could then place it in my main rout like this

js
app.get('/', helloWorld, (req, res) =>{
console.log('get recieved');
})

Then when I go to / and look at the console I would see 'Hello World' printed out followed by 'get received'.

Error handling ​

This is how express catches & handles errors, It basically operates as a middleware on its own but using the (err, req, res, next) inputs rather than (req, res, next).

Conclusion ​

Express is a nodejs framework that is lightweight and extensible with the essential tools needed for a website and the ability to add and build your own through middleware

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