JSFiddle - React, Tailwind, and code Playground

HTML

<input type="submit" value="Alert" class="alertButton"/>
    
  

<table class="resultGridTable" cellspacing="0" id="detailContentPlaceholder_grdLocalTaxReport"
    style="border-collapse: collapse;">
    <tr>
        <th scope="col">
            IsSummaryRow
        </th>
        <th scope="col">
            Associate
        </th>
        <th scope="col">
            Gross Amount
        </th>
        <th scope="col">
            Federal Withholding
        </th>
        

    </tr>
    <tr>
        <th scope="col">
            False
        </th>
        <td>
            Norman Tylor
        </td>
        <td>
            3450
        </td>
        <td>
            32
        </td>
    </tr>
</table>

    <script type="text/javascript" src="http://ajax.aspnetcdn.com/ajax/jquery/jquery-1.4.1.js"></script>

CSS

td
{
    margin: 0 10px 0 10px;
    border: 1px solid orange;
}

th
{
    margin: 0 10px 0 10px;
    border: 1px solid purple;
   
}

JavaScript

$('.alertButton').click(function()
{
                                                  
    var selectedElements = $("th:first");
    selectedElements.css('background-color','yellow');
    alert(selectedElements.html());

                        
});