JSFiddle - React, Tailwind, and code Playground

HTML

<table>
	<tbody>
		<tr id="day-0">
			<td>Maandag</td>
		</tr>
		<tr id="day-1">
			<td>Dinsdag</td>
		</tr>
		<tr id="day-2">
			<td>Woensdag</td>
		</tr>
		<tr id="day-3">
			<td>Donderdag</td>
		</tr>
		<tr id="day-4">
			<td>Vrijdag</td>
		</tr>
		<tr id="day-5">
			<td>Zaterdag</td>
		</tr>
		<tr id="day-6">
			<td>Zondag</td>
		</tr>
	</tbody>
</table>

CSS

.today { 
  background-color: #FFD700 !important; 
}

table {
	border-collapse: collapse;
	width: 100%;
	border-spacing: 0;
	margin: .5em 0;
}

th, td {
	padding: 1em;
	text-align: left;
	border-bottom: 1px solid #ddd;
	border-color:black;
	border-style:solid;
	border-width:1px;
	overflow:hidden;
	word-break:normal;
}

tr:hover {background-color: #EEE}

JavaScript

workday();

function workday() {
  var d = new Date().getDay();
  document.getElementById("day-"+d).classList.add('today');    
}