node express helloworld
var express = require('express');
var app = express();
app.get('/', function(req, res) {
res.send("Hello World!");
});
var server = app.listen(3000, function() {
var host = server.address().address;
var port = server.address().port;
console.log('Hello World app listening at http://%s:%s', host, port);
});