add js for files view

web/skins/classic/views/js/files.js

@@ -0,0 +1,28 @@
+function setButtonStates(element) {
+  const form = document.getElementById('filesForm');
+
+  if (canEdit.System) {
+    let disabled = true;
+
+    const files = len=form.elements['files[]'];
+    if (files) {
+      for (let i=0, len=files.length; i<len; i++) {
+        if (files[i].checked) {
+          disabled = false;
+          break;
+        }
+      }
+    }
+    form.elements['action'].disabled = disabled;
+  } else {
+    form.elements['action'].disabled = true;
+  }
+}
+
+function initPage() {
+  setButtonStates();
+  document.querySelectorAll('input[name="files[]"]').forEach(function(el) {
+    el.onclick=setButtonStates;
+  });
+}
+$j(document).ready(initPage );