JSFiddle - React, Tailwind, and code Playground

by Tilwin Joy

HTML

<div class="main">
    <table>
        <tr>
            <td>row1 column1</td>
            <td>
                <div class="pRelative">
                    <div class="pAbsolute dropdown">
                        <div class="option">Zero</div>
                        <div class="option">One</div>
                        <div class="option">Two</div>
                        <div class="option">Three</div>
                        <div class="option">Four</div>
                        <div class="option">Five</div>
                        <div class="option">Six</div>
                    </div>
                </div>
            </td>
            <td>row1 column3</td>
        </tr>
        <tr>
            <td>row2 column1</td>
            <td>row2 column2</td>
            <td>row2 column3</td>
        </tr>
        <tr>
            <td>row3 column1</td>
            <td>row3 column2</td>
            <td>row3 column3</td>
        </tr>
        <tr>
            <td>row4 column1</td>
            <td>row4 column2</td>
            <td>row4 column3</td>
        </tr>
        <tr>
            <td>row5 column1</td>
            <td>row5 column2</td>
            <td>row5 column3</td>
        </tr>
        <tr>
            <td>row6 column1</td>
            <td>row6 column2</td>
            <td>row6 column3</td>
        </tr>
        <tr>
            <td>row7 column1</td>
            <td>row7 column2</td>
            <td>row7 column3</td>
        </tr>
        <tr>
            <td>row8 column1</td>
            <td>row8 column2</td>
            <td>row8 column3</td>
        </tr>
    </table>
</div>

CSS

.main {
    height: 100px;
    overflow-y: scroll;
    overflow-x: hidden;
    margin-top: 100px;
    opacity:.99;
}
.pRelative {
    position: relative;
}
.pAbsolute {
    position: fixed;
}
.dropdown {
    width: 100px;
    background-color: cornflowerblue;
    z-index: 1000;
}
.option {
    border-top: 1px solid green;
    border-bottom: 1px solid green;
}
table td {
    border: 1px solid black;
    padding: 10px;
}

JavaScript

var main = document.getElementsByClassName('main')[0];
var dd = document.getElementsByClassName('pAbsolute')[0];
var offset = dd.getBoundingClientRect().top;
main.onscroll = function () {
    var st = main.scrollTop;
    ddt = (offset - st);
    dd.style.top = ddt + 'px';
}