code: function() {
      this.WHERE_OPTIONS =
          [[Blockly.Msg.TEXT_CHARAT_FROM_START, 'FROM_START'],
           [Blockly.Msg.TEXT_CHARAT_FROM_END, 'FROM_END'],
           [Blockly.Msg.TEXT_CHARAT_FIRST, 'FIRST'],
           [Blockly.Msg.TEXT_CHARAT_LAST, 'LAST'],
           [Blockly.Msg.TEXT_CHARAT_RANDOM, 'RANDOM']];
      this.setHelpUrl(Blockly.Msg.TEXT_CHARAT_HELPURL);
      this.setColour(Blockly.Blocks.texts.HUE);
      this.setOutput(true, 'String');
      this.appendValueInput('VALUE')
          .setCheck('String')
          .appendField(Blockly.Msg.TEXT_CHARAT_INPUT_INTEXT);
      this.appendDummyInput('AT');
      this.setInputsInline(true);
      this.updateAt_(true);
      this.setTooltip(Blockly.Msg.TEXT_CHARAT_TOOLTIP);
    }
docs: Block for getting a character from the string.
  @this Blockly.Block