xmlhttp.onreadystatechange = function()

in code/app/static/main.js [141:155]


    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == XMLHttpRequest.DONE) {   // XMLHttpRequest.DONE == 4
           if (xmlhttp.status == 204) {
                sendAlert("Image Deleted.");  
                listImages();
           }
           else if (xmlhttp.status == 400) {
              alert('There was an error 400');
           }
           else {
               alert('something else other than 204 was returned');
               console.log(xmlhttp.status);
           }
        }
    };