JSFiddle - React, Tailwind, and code Playground

HTML

<table border="2" id="aTable">
    <tr>
        <td>First</td>
        <td>A</td>
        <td>AA</td>
    </tr>
    <tr>
        <td>First</td>
        <td>A</td>
        <td>B</td>
    </tr>
    <tr>
        <td>Second</td>
        <td>V</td>
        <td>sV</td>
    </tr>
    <tr>
        <td>Third</td>
        <td>D</td>
        <td>D</td>
    </tr>
    <tr>
        <td>Third</td>
        <td>E</td>
        <td>E</td>       
    </tr>
</table>

JavaScript

var seen = {};
$('#aTable td').each(function() 
{
    var $this = $(this);
    var index = $this.index();
    var txt =  $this.text();
    if (seen[index] === txt) 
    {
        $($this.parent().prev().children()[index]).attr('rowspan', 2);
        $this.hide();
    }
    else 
    {
        seen[index] = txt;
    }
});