xmlhttp.onreadystatechange = function()

in code/client/static/js/main.js [188:201]


    xmlhttp.onreadystatechange = function() {
        if (xmlhttp.readyState == XMLHttpRequest.DONE) {   // XMLHttpRequest.DONE == 4
           if (xmlhttp.status == httpStatusCreated) {
                listTrainer()
           }
           else if (xmlhttp.status == httpStatusBadRequest) {
              alert('There was an error httpStatusBadRequest');
           }
           else {
               alert('something else other than httpStatusCreated was returned');
               console.log(xmlhttp.status);
           }
        }
    };