result

client-side:
	var keys = {a:1,b:2};
	var formdata = new FormData();
	formdata.append("keys", JSON.stringify(keys));
	var ajax = new XMLHttpRequest();
	ajax.open("POST", window.location.pathname);
	ajax.send(formdata);

server-side:
	app.use(bodyParser.urlencoded({ extended: false }));
	app.use(bodyParser.json());
	...
	console.log(request.body.keys); //expected [Object Object] ({a:1,b:2}), result: undefined
	console.log(request.body); //actual result "{}"