Empezando con express

npm i express

var express = require('express');
var app = express();

app.get('/', function (req, res) {
  res.send('Hello World!');
});

app.listen(3000, function () {
  console.log('Example app listening on port 3000!');
});

The general syntax for a route is shown below

app.METHOD(PATH, HANDLER)
Wherein,

1) app is an instance of the express module

2) METHOD is an HTTP request method (GET, POST, PUT or DELETE)

3) PATH is a path on the server.

4) HANDLER is the function executed when the route is matched

var express = require('express');
var app = express();
app.route('/Node').get(function(req,res)
{
    res.send("Tutorial on Node");
});
app.route('/Angular').get(function(req,res)
{
    res.send("Tutorial on Angular");
});
app.get('/',function(req,res){
    res.send('Welcome to Guru99 Tutorials');
}));

app.get("/items/:vegetable", (req, res) => {
let veg = req.params.vegetable;
res.send(`This is the page for ${veg}`);
});

middleware:

app.use((req, res, next) => {
console.log(`request made to: ${req.url}`);
next();
});

// An example middleware function
var a_middleware_function = function(req, res, next) {
  // ... perform some operations
  next(); // Call next() so Express will call the next middleware function in the chain.
}

// Function added with use() for all routes and verbs
app.use(a_middleware_function);

// Function added with use() for a specific route
app.use('/someroute', a_middleware_function);

// A middleware function added for a specific HTTP verb and route
app.get('/', a_middleware_function);

Para archivos estáticos:

app.use(express.static('public'));