NodeJS - create express server on button click event

I'm beginner to Node, I just need to create a express server on a button click event, I did as below but it shouldn't work

script.js

$('#button').click(function(){
    $.post('/test');
});

app.js

app.post('/test', function (req, res) {

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

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

    var server = app.listen(3100, function () {
    var host = server.address().address
    var port = server.address().port 
  })
});

via slokuliyana