code: function() {
      // Assign 'this' to a variable for use in the closures below.
      var thisBlock = this;
      var dropdown = new Blockly.FieldDropdown(
          [[Blockly.Msg.LISTS_SPLIT_LIST_FROM_TEXT, 'SPLIT'],
           [Blockly.Msg.LISTS_SPLIT_TEXT_FROM_LIST, 'JOIN']],
          function(newMode) {
            thisBlock.updateType_(newMode);
          });
      this.setHelpUrl(Blockly.Msg.LISTS_SPLIT_HELPURL);
      this.setColour(Blockly.Blocks.lists.HUE);
      this.appendValueInput('INPUT')
          .setCheck('String')
          .appendField(dropdown, 'MODE');
      this.appendValueInput('DELIM')
          .setCheck('String')
          .appendField(Blockly.Msg.LISTS_SPLIT_WITH_DELIMITER);
      this.setInputsInline(true);
      this.setOutput(true, 'Array');
      this.setTooltip(function() {
        var mode = thisBlock.getFieldValue('MODE');
        if (mode == 'SPLIT') {
          return Blockly.Msg.LISTS_SPLIT_TOOLTIP_SPLIT;
        } else if (mode == 'JOIN') {
          return Blockly.Msg.LISTS_SPLIT_TOOLTIP_JOIN;
        }
        throw 'Unknown mode: ' + mode;
      });
    }
docs: Block for splitting text into a list, or joining a list into text.
  @this Blockly.Block