JSFiddle - React, Tailwind, and code Playground

HTML

<input type="checkbox" class="testmethod" id="beastmode" name="beastmode" tabindex="5">Beast Mode</input>

    <div class="input-group date" id="id_1">
          <input type="text" name="day11" value="09:00 AM" class="form-control"
              placeholder="End time" title="" required/>
            <div class="input-group-addon input-group-append">
                  <div class="input-group-text">
                       <i class="glyphicon glyphicon-time fa fa-clock-o"></i>
                  </div>
            </div>
        </div>

CSS

#id_1,#id_2 {
  display: none;
}

JavaScript

$("#beastmode").click(function () {
        if ($(this).prop('checked') === true) {
            $('#id_1,#id_2').show();
        } else {
            $('#id_1,#id_2').hide();
        }
    });