Express.js in 5 mintues | Node.js

npm install express

my fist HelloWorld application.

var express=require('express');    //use the express module
var app=express();     // create an object of express module
app.get('/', function (req,res){ //create a call back function
    res.send('helloworld'); //send helloworld response
});
var server = app.listen(3000, function(){ make the server listen on 3000
   
});

----

1. using require function we are including the express module.
2. we need to make an object for the express module we just included.
3. create a callback function to be called whenever the user hits our root (/)
4. in the callback function, we are sending a response to the user
5. call a listen to function to make our server listens to client requests on port 3000.
done. use this web address to confirm.
localhost:3000/

Route (/):
routes reads clients input and responds to the request. say GET,POST,PUT,Delete

localhost:3000/
localhost:3000/books
localhost:3000/students

in above,
we used get method (app.get while calling a callback function)
the syntax was like this:
app.METHOD( PATH, HANDLER)

the app is an instance of express
the method is an HTTP request method like GET, POST, PUT, DELETE)
PATH is a path on the server, like route (/), /books
HANDLER is the call back function executed when the route is matched.

let's look with 3 examples:
/node route will display "hello node"
/angular route will display "hello angular"
/ route will display "hello buddy"

app.route('/node', get(function(req,res){
    res.send("hello node");
} ));
app.route('/angular', get(function(req,res){
    res.send("hello angualr");
});
app.get('/',(function(req,res){
    res.sed("hello buddy");
});