JSFiddle - React, Tailwind, and code Playground

HTML

<div class="data">    
<span>
<input name="employee" type="checkbox" value="Alex"/>
<label for="employee">Alex</label>
</span> 

<span>
<input name="employee" type="checkbox" value="Frank"/>
<label for="employee">Frank</label>
</span>    

<span>
<input name="employee" type="checkbox" value="Mark"/>
<label for="employee">Mark</label>
</span>
</div>

JavaScript

$('input').on('click', function(){
var selected = [];
$('.data input:checked').each(function() {
     selected.push($(this).val());
});


//Or
/*
var checkboxes = document.getElementsByName('employee');
var selected = [];
  for (var i=0; i<checkboxes.length; i++) {
     if (checkboxes[i].checked) {
        selected.push(checkboxes[i].value);
     }
  }
*/
  alert(selected);
});