js/tinymce/tinymce.jquery.js
function () {
          var level;

          if (self.typing) {
            self.add();
            self.typing = false;
            setTyping(false);
          }

          if (index > 0) {
            level = data[--index];
            Levels.applyToEditor(editor, level, true);
            setDirty(true);
            editor.fire('undo', { level: level });
          }

          return level;
        }
function () {
          var level;

          if (self.typing) {
            self.add();
            self.typing = false;
            setTyping(false);
          }

          if (index > 0) {
            level = data[--index];
            Levels.applyToEditor(editor, level, true);
            setDirty(true);
            editor.fire('undo', { level: level });
          }

          return level;
        }
function ( ) { var level ; if ( self . typing ) { self . add ( ) ; self . typing = false ; setTyping ( false ) ; } if ( index > 0 ) { level = data [ -- index ] ; Levels . applyToEditor ( editor , level , true ) ; setDirty ( true ) ; editor . fire ( 'undo' , { level : level } ) ; } return level ; }
Undoes the last action.

@method undo
@return {Object} Undo level or null if no undo was performed.
Undoes the last action .