JSFiddle - React, Tailwind, and code Playground

HTML

<table class="mable">
<tr class="t"><td>4</td></tr>
<tr class="t"><td>3</td></tr>
<tr class="t"><td>2</td></tr>
<tr class="t"><td>1</td></tr>
</table>
<table class="mable">
<tr class="t"><td>3</td></tr>
<tr class="t"><td>2</td></tr>
<tr class="t"><td>1</td></tr>
</table>
<table class="mable">
<tr class="t"><td>2</td></tr>
<tr class="t"><td>1</td></tr>
</table>

JavaScript

$('.mable').each(function(){

    tr_count=$(this).attr('tr').length;
    alert(tr_count);
});