exampleserver.js

var http = require("http");
var url = require("url");
var fs = require("fs");

var router = {
	"/" : function() {
		return "Home"
	},
	"/submit" : function (request) {
		// write submitted info to file
		writeNewUser(request.parsedUrl, function(){
			console.log("done writing file");
		});
		console.log("returning body now");
		return "Submit"
	}
}

var server = http.createServer(function (request, response) { 
	logRequest(request);

	request.parsedUrl = url.parse(request.url, true);
	
	var bodyHandler = router[request.parsedUrl.pathname];

	if (bodyHandler) {
		response.statusCode = 200;
		response.write(bodyHandler(request));
		response.end();
	} else {
		response.statusCode = 404;
		response.end("Not Found");
	}
});

function writeNewUser(user, callback) {
	//first line
	fs.readFile('./db.csv', function (err, fileData) {
		//second line
		if (err) throw err;
		//third line
		var fileWithConcatenatedData = fileData.toString() + user + "\n";
		fs.writeFile('./db.csv', fileWithConcatenatedData, function(err){
			//last line
			callback(err)
		});
	});
}

function logRequest (request) {
	console.log(request.url);
}

server.listen(3000); // listen on port 3000