[niko42]

function handleFiles(files) {
        for (var i = 0; i < files.length; i++) {
            var file = files[i];
            var imageType = /image.*/;

            if (!file.type.match(imageType)) {
                continue;
            }

            var img = document.createElement("img");
            img.classList.add("obj");
            img.file = file;
            $('#file').before(img); // Assuming that "preview" is a the div output where the content will be displayed.

            var reader = new FileReader();
            reader.onload = (function(aImg) { return function(e) { aImg.src = e.target.result; }; })(img);
            reader.readAsDataURL(file);

            var form = new FormData();
            form.append('photoCategory', file);

            var xhr = new XMLHttpRequest();
            xhr.onload = function(data) {
                console.log(data.currentTarget.responseText);
                console.log("Отправка завершена");
            };
            xhr.open("post", "/adminpro/File_Upload", true);
            xhr.send(form);
        }
    }

Спасибо!