JSFiddle - React, Tailwind, and code Playground

HTML

<table>
<tr id="21.30---22.00">
    <td class='51'>Text</td>
</tr>
</table>

JavaScript

$(document).ready(function(){
    var time = "21.30---22.00";
    time = time.replace(/\./g,'\\.');
    $("tr#" + time + " td.51").css("color","blue");
});