JSFiddle - React, Tailwind, and code Playground

HTML

<body>

<div id="wrapper">

<table class="table1">

<tr>

<td><select name="tasks" id="tasks">
        <option value="">Tasks</option>
                <option value="1">1</option>
                <option value="2">2</option>
                <option value="3">3</option>
                <option value="4">4</option>
                <option value="5">5</option>
                <option value="6">6</option>
                <option value="7">7</option>
                <option value="8">8</option>
                <option value="9">9</option>
                <option value="10">10</option>

</select>   
</td>
<td class="days">Monday</td>
<td class="days">Tuesday</td>
<td class="days">Wednesday</td>
<td class="days">Thursday</td>
<td class="days">Friday</td>
<td class="days">Saturday</td>
<td class="days">Sunday</td>
</tr>

<tr class="row">
<td> 1 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 2 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 3 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 4 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 5 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 6 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 7 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 8 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 9 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

<tr class="row">
<td> 10 </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
<td> </td>
</tr>

</table>

</div>

CSS

table,td {
    border:1px solid #999;
}

td {
    width:150px;
}

JavaScript

$("#tasks").change(function () {
    // Convert 1-based index to 0 based index
    var index = this.value - 1;
    
    // Select all rows in the table
    var $rows = $('.row', '.table1');
    
    // Set all rows to no background
    $rows.css('background-color', '');
    
    // Change the selected row's color to one
    $('.row', '.table1').eq(index).css('background-color', 'yellow');
});