Node / Express parsed JSON POST is not valid JSON

I am making a JSON POST request using XMLHttpRequest, however Express appears to wrap the received JSON in an additional object, how can I prevent this ?

This is the client sending the JSON data:

var xhr = new XMLHttpRequest();
xhr.open("POST", "https://mydev.puremfg.net/",true);

// This header MUST be present for POST requests.
xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
xhr.setRequestHeader("Accept", "application/json, text/javascript");
var jarr = {"hxx":1};
xhr.send(JSON.stringify({"hxx":1}));

And this is Nodejs / Express middleware:

app.use(function(req, res, next){
    fn.console.log(req.body);
   })

This is the output:

   { '{"hxx":1}': '' }

via crankshaft