Simple Native AJAX

nativeAJAX.js

var data= {var:"val"}
xhr = new XMLHttpRequest();

xhr.open('POST', 'url');
xhr.setRequestHeader('Content-Type', 'application/json');
xhr.onload = function() {
    if (xhr.status === 200){
        console.log(xhr.responseText);
    }else if (xhr.status !== 200){
        console.log('Failed ' + xhr.status);
    }
};
xhr.send(JSON.stringify(data));