JSFiddle - React, Tailwind, and code Playground

HTML

<div>
<table>
        <tr><th class="headcol">1</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">2</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">3</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">4</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">5</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">6</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">1</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">2</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">3</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">4</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">5</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">6</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr><tr><th class="headcol">1</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th class="headcol">2</th><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td><td class="long">QWERTYUIOPASDFGHJKLZXCVBNM</td></tr>
        <tr><th...

CSS

table { border-collapse:separate; border-spacing:0;border-top: 1px solid grey; }
        td, th {
            margin:0;
            border:1px solid grey;
            white-space:nowrap;
            border-top-width:0px;
        }
        div {
            width: 500px;
            height:500px;
            overflow-x:scroll;  
            margin-left:5em;
            overflow-y:visible;
            padding:0;
        }
        .headcol {
            position:absolute;
            width:5em;
            left:0;
            top:auto;
            border-top-width:1px; /*only relevant for first row*/
            margin-top:-1px; /*compensate for top border*/
        }
        .headcol:before {content: 'Row ';}
        .long { background:yellow; letter-spacing:1em; }