anchor.diff:  
   $(function() {
   
  -  var openDialog = function(name, initialFilename, okInitiallyDisabled, okClicked) {
  -    var input = makeInput(name, initialFilename);
  -    var ok = {
  +  const openDialog = function(name, initialFilename, okInitiallyDisabled, okClicked) {
  +    const input = makeInput(name, initialFilename);
  +    const ok = {
         text: 'ok',
         id: 'file-ok',
         disabled: okInitiallyDisabled,
         click: function() {
  -        var newFilename = $.trim(input.val());
  +        const newFilename = $.trim(input.val());
           okClicked(newFilename);
           $(this).remove();
         }
       };
  -    var cancel = {
  +    const cancel = {
         text: 'cancel',
         click: function() { $(this).remove(); }
       };
  -    var div = $('<div>');
  +    const div = $('<div>');
       div.append(input);
  -    var fileOperationDialog = div.dialog({
  +    const fileOperationDialog = div.dialog({
         closeOnEscape: true,
         close: function() { $(this).remove(); },
     	  title: cd.dialogTitle(name + '&nbsp;file'),
  
positive.code:     return true;
    };
  
    var fileButtons =  $('#file-operations');
    var newFile = fileButtons.find('#new');
    var renameFile = fileButtons.find('#rename');
    var deleteFile = fileButtons.find('#delete');
  
    newFile.click(function() {
      var initialFilename = 'filename' + cd.extensionFilename();
      var okInitiallyDisabled = !isValidFilename(initialFilename);
      var okClicked = function(filename) {
        cd.newFileContent(filename, '');
        cd.loadFile(filename); // hack to get focus
      };
      openDialog('new', initialFilename, okInitiallyDisabled, okClicked);
    });
  
    renameFile.click(function() {
      var initialFilename = cd.currentFilename();
      var okInitiallyDisabled = true;
      var okClicked = function(filename) {
        renameFileFromTo(initialFilename, filename);
      };
      openDialog('rename', initialFilename, okInitiallyDisabled, okClicked);
    });
  
    deleteFile.click(function() {
      var initialFilename = cd.currentFilename();
      var okInitiallyDisabled = false;
      var okClicked = function(filename) {
        cd.deleteFile(filename);
      };
      openDialog('delete', initialFilename, okInitiallyDisabled, okClicked);
  
negative.code:       buttons: [ ok, cancel ]
      });
    	input.keyup(function(event) {
        const ok = $('#file-ok');
        const newFilename = $.trim(input.val());
        event.preventDefault();
        if (isValidFilename(newFilename))  {
          ok.button('enable');
  