JSFiddle - React, Tailwind, and code Playground

by jfriend00

HTML

<table border="0" cellspacing="5" cellpadding="5" id="tbl">
        <tr><th>Header</th></tr>
        <tr><td>Data 1</td></tr>
        <tr><td>Data 2</td></tr>
        <tr><td>Data 3</td></tr>
        <tr id="start"><td>Data 4</td></tr>
    </table>

JavaScript

function getRowIndex(elem) {
    var index = 0;
    while (elem = elem.previousSibling) {
        if (elem.tagName == "TR") {
            ++index;
        }
    }
    return(index);
}    

var elem = document.getElementById("start");
alert(getRowIndex(elem));