JSFiddle - React, Tailwind, and code Playground

HTML

<ul role="menu" class="dropdown-menu" id="comp">

  <li>
    <a href="#">
      <input type="checkbox" id="a1">
      <span class="lbl"> Monday</span>
    </a>
  </li>
  <li>
    <a href="#">
      <input type="checkbox" id="a2">
      <span class="lbl"> Tuesday</span>
    </a>
  </li>
  <li>
    <a href="#">
      <input type="checkbox" id="a3" checked="checked">
      <span class="lbl"> Wednesday</span>
    </a>
  </li>
  <li>
    <a href="#">
      <input type="checkbox" id="a4">
      <span class="lbl"> Thursday</span>
    </a>
  </li>
  <li>
    <a href="#">
      <input type="checkbox" id="a5">
      <span class="lbl"> Friday</span>
    </a>
  </li>


</ul>

JavaScript

$(function() {
  var checkedItems = $("#comp input:checked");
  console.log(checkedItems);
  $("#comp input[type='checkbox']").change(function() {
    if ($(this).attr("checked") == "checked") {
      checkedItems.push($(this)[0]);
      console.log(checkedItems);
    } else {
      checkedItems.splice($.inArray($(this)[0], checkedItems), 1);
      console.log(checkedItems);
    }
  })
})