How to send parameters to the server side in io.js (nodejs) with ajax

iojs-ajax

// This snippet demonstrates how to send a json object to the server
// and how to retrieve it from the server side to save it in a file

// CLIENT SIDE : PAGE.JS
// ---------------------
// Save stats to a file to retrieve values later
function saveToFile() {
    var jsonArray = JSON.stringify(_stats);
    console.log(jsonArray);
    jsonArray = encodeURIComponent(jsonArray);

    // Send an Ajax request to the server
    // $.post('/counters/save', jsonArray, function (response) {
    //     console.log("totorr");
    // });

    var xhr = new XMLHttpRequest();
    xhr.open('POST', '/counters/save?json=' + jsonArray, true);
    xhr.setRequestHeader('Content-type', 'application/x-www-form-urlencoded');
    xhr.send(null);

    xhr.onreadystatechange = function() {
        if (xhr.readyState == 4 && xhr.status == 200) {
            console.log("Data correctly saved!");
        }
    }
}



// SERVER SIDE : SERVER.JS
// -----------------------
// Starts with the require to get modules
var express 		= require('express'),	// web dev framework
    jf				= require('jsonfile'),
	  util			= require('util');

// The app's configuration
app.use(bodyParser());
app.use(bodyParser.json());				// to suport JSON-encoded bodies
app.use(bodyParser.urlencoded({			// to suport URL-encoded bodies
	extended: true
}));

// Create an app object
// assuming you have node and express framework installed
var app = express();

// A POST url
app.post('/counters/save', function (req, res) {
	// Save the values to a local file
  // Set the path to save the file
	var file = __dirname + '/public/modules/counters/data.json'; // enter your path
	
  // 	Get the json object contained in the url
	var obj = req.query.json;

  // Write in the file
	jf.writeFile(file, obj, function (err) {
		console.log(err);
	});

	res.send(200);
});