function readSingleFile(evt) {
            var f = evt.target.files[0];
            var r = new FileReader();
            if (f) {
              r.onload = function(e) {
                var contents = e.target.result;
                var allText = JSON.parse(contents);
                console.log(llText.toString());
              }
              r.readAsText(f);
              console.log(r.result);
            } else {
              alert("Failed to load file");
            }
        }