[upload] give filesize-tracker script some polish

ext/upload/script.js

@@ -0,0 +1,56 @@
+function fileSize(size) {
+    var i = Math.floor(Math.log(size) / Math.log(1024));
+    return (size / Math.pow(1024, i)).toFixed(2) * 1 + ['B', 'kB', 'MB', 'GB', 'TB'][i];
+}
+function updateTracker() {
+    var size = 0;
+    var upbtn = document.getElementById("uploadbutton");
+    var tracker = document.getElementById("upload_size_tracker");
+    var lockbtn = false;
+
+    // check that each individual file is less than the max file size
+    document.querySelectorAll("#large_upload_form input[type='file']").forEach((input) => {
+        var cancelbtn = document.getElementById("cancel"+input.id);
+        var toobig = false;
+        if (input.files.length) {
+            if(cancelbtn) cancelbtn.style.visibility = 'visible';
+            for (var i = 0; i < input.files.length; i++) {
+                size += input.files[i].size;
+                if (window.shm_max_size > 0 && input.files[i].size > window.shm_max_size) {
+                    toobig = true;
+                }
+            }
+            if (toobig) {
+                lockbtn = true;
+                input.style = 'color:red';
+            } else {
+                input.style = 'color:initial';
+            }
+        } else {
+            if(cancelbtn) cancelbtn.style.visibility = 'hidden';
+            input.style = 'color:initial';
+        }
+    });
+
+    // check that the total is less than the max total size
+    if (size) {
+        tracker.innerText = fileSize(size);
+        if (window.shm_max_total_size > 0 && size > window.shm_max_total_size) {
+            lockbtn = true;
+            tracker.style = 'color:red';
+        } else {
+            tracker.style = 'color:initial';
+        }
+    } else {
+        tracker.innerText = '0MB';
+    }
+    upbtn.disabled = lockbtn;
+}
+document.addEventListener('DOMContentLoaded', () => {
+    if(document.getElementById("upload_size_tracker")) {
+        document.querySelectorAll("#large_upload_form input[type='file']").forEach((el) => {
+            el.addEventListener('change', updateTracker);
+        });
+        updateTracker();    
+    }
+});