old_contents: /* global $ */
  
  (function (window, document, $) {
      'use strict';
  
      var LiveEditorToolbar = function LiveEditorToolbar (params) {
          this.init(params);
      };
  
      LiveEditorToolbar.prototype.init = function (params) {
          this.$appendTo = params.$appendTo;
          this.create();
      };
  
      LiveEditorToolbar.prototype.create = function () {
          this.$modeSelect = $('<select class="form-control">')
                                  .append('<option value="edit">Edit mode</option>')
                                  .append('<option value="view">View mode</option>');
          this.$buttonAddOption = $('<button class="add-option" type="button">+ add option</button>');
          this.$undoButton = $('<button type="button" class="btn btn-default btn-undo">Undo</button>');
          this.$codePanelButton = $('<button class="btn btn-primary btn-sm code-panel-button" type="button" data-toggle="collapse" data-target="#code-panel">').text('< edit code >');
          this.$toolbar = $('<ul class="toolbar">');
  
          this.$toolbar.append($('<li>').append(this.$buttonAddOption));
          this.$toolbar.append($('<li>').append(this.$modeSelect));
          this.$toolbar.append($('<li>').append(this.$undoButton));
          this.$toolbar.append($('<li>').append(this.$codePanelButton));
  
          this.$appendTo.append(this.$toolbar);
      }
  
      window.LiveEditorToolbar = LiveEditorToolbar;
  })(window, document, $);
new_contents: /* global $ */
  
  (function (window, document, $) {
      'use strict';
  
      var LiveEditorToolbar = function LiveEditorToolbar (params) {
          this.init(params);
      };
  
      LiveEditorToolbar.prototype.init = function (params) {
          this.$appendTo = params.$appendTo;
          this.create();
      };
  
      LiveEditorToolbar.prototype.create = function () {
          this.$modeSelect = $('<select class="form-control">')
                                  .append('<option value="edit">Edit mode</option>')
                                  .append('<option value="view">View mode</option>');
          this.$buttonAddOption = $('<button type="button" class="btn btn-default add-option">+ add option</button>');
          this.$undoButton = $('<button type="button" class="btn btn-default btn-undo">Undo</button>');
          this.$codePanelButton = $('<button class="btn btn-primary btn-sm code-panel-button" type="button" data-toggle="collapse" data-target="#code-panel">').text('< edit code >');
          this.$toolbar = $('<ul class="toolbar">');
  
          this.$toolbar.append($('<li>').append(this.$buttonAddOption));
          this.$toolbar.append($('<li>').append(this.$modeSelect));
          this.$toolbar.append($('<li>').append(this.$undoButton));
          this.$toolbar.append($('<li>').append(this.$codePanelButton));
  
          this.$appendTo.append(this.$toolbar);
      };
  
      window.LiveEditorToolbar = LiveEditorToolbar;
  })(window, document, $);
subject: Add css to add-option button