code: function toggleFullScreen(editor) {
      // Set fullscreen
      var cm = editor.codemirror;
      cm.setOption('fullScreen', !cm.getOption('fullScreen'));
  
  
      // Prevent scrolling on body during fullscreen active
      if (cm.getOption('fullScreen')) {
          saved_overflow = document.body.style.overflow;
          document.body.style.overflow = 'hidden';
      } else {
          document.body.style.overflow = saved_overflow;
      }
  
  
      // Update toolbar class
      var wrap = cm.getWrapperElement();
  
      if (!/fullscreen/.test(wrap.previousSibling.className)) {
          wrap.previousSibling.className += ' fullscreen';
      } else {
          wrap.previousSibling.className = wrap.previousSibling.className.replace(/\s*fullscreen\b/, '');
      }
  
  
      // Update toolbar button
      if (editor.toolbarElements.fullscreen) {
          var toolbarButton = editor.toolbarElements.fullscreen;
  
          if (!/active/.test(toolbarButton.className)) {
              toolbarButton.className += ' active';
          } else {
              toolbarButton.className = toolbarButton.className.replace(/\s*active\s*/g, '');
          }
      }
  
  
      // Hide side by side if needed
      var sidebyside = cm.getWrapperElement().nextSibling;
      if (/editor-preview-active-side/.test(sidebyside.className))
          toggleSideBySide(editor);
  }
docs: Toggle full screen of the editor.