JSFiddle - React, Tailwind, and code Playground

HTML

<table>
  <tr class="header first test1">
    <th>Month</th>
    <th>Savings</th>
  </tr>
  <tr class="header first test2">
    <td>January</td>
    <td>$100</td>
  </tr>
  <tr class="h34der third test1">
    <td>February</td>
    <td>$80</td>
  </tr>
</table>

CSS

table, th, td {
    border: 1px solid black;
}

JavaScript

$(document).ready(function(){
	$('.header, .test1').css('background','yellow');
});