JSFiddle - React, Tailwind, and code Playground

HTML

<table border="1" id="myTable">
			<tr>
				<td>Mon</td>
				<td>Tues</td>
				<td>Wed</td>
			</tr>
			<tr>
				<td class="ws_is_single_day_header">
					<div class="demo-class">Event 1</div>
					<div class="demo-class ws_is_all_day_event">Event 2</div>
					<div class="demo-class">Event 3</div>
				</td>
				<td class="ws_is_single_day_header">
					<div class="demo-class">Event 1</div>
					<div class="demo-class">Event 2</div>
					<div class="demo-class">Event 3</div>
					<div class="demo-class">Event 1</div>
					<div class="demo-class">Event 2</div>
					<div class="demo-class">Event 3</div>
				</td>
				<td class="ws_is_single_day_header">
					<div class="demo-class">Event 1</div>
					<div class="demo-class">Event 3</div>
				</td>
			</tr>
		
		</table>

CSS

.ws_is_all_day_event
{
    background-color:red;
}
.ws_has_all_day_event
{
background-color:green;
}

JavaScript

$(function(){   
    $('#myTable tr td div').each(function () {		
			 
        if($(this).hasClass("demo-clas"))
        {
        alert($(this));
        }
			
    });
});