JSFiddle - React, Tailwind, and code Playground

HTML

<table>
    <tr>
        <td>A1</td>
        <td>A2</td>
        <td>A3</td>
    </tr>
    <tr>
        <td>B1</td>
        <td>B2</td>
        <td>B3</td>
    </tr>
    <tr>
        <td>C1</td>
        <td>C2</td>
        <td>C3</td>
    </tr>
</table>

CSS

tr.highlighted td {
    background: red;
}
tr:after {
    border-bottom: 60px solid transparent;
    border-left: 60px solid green;
    border-top: 60px solid transparent;
    height: 0;
    width: 0;
    float:right;
}

JavaScript

document.querySelector('table').onclick = highlight;

function highlight(e) {
    e = e || event;
    var from = findrow(e.target || e.srcElement),
        highlighted = /highlighted/i.test((from || {}).className);
    if (from) {
        var rows = from.parentNode.querySelectorAll('tr');
        for (var i = 0; i < rows.length; i += 1) {
            rows[i].className = '';
        }
        from.className = !highlighted ? 'highlighted' : '';
    }
}

function findrow(el) {
    if (/tr/i.test(el.tagName)) return el;
    var elx;
    while (elx = el.parentNode) {
        if (/tr/i.test(elx.tagName)) {
            return elx;
        }
    }
    return null;
}