The rowIndex read-only property of the HTMLTableRowElement interface represents the position of a row within the whole <table>.
Even when the <thead>, <tbody>, and <tfoot> elements are out of order in the HTML, browsers render the table in the right order. Therefore the rows count from <thead> to <tbody>, from <tbody> to <tfoot>.
The index of the row, or -1 if the row is not part of a table.
This example uses JavaScript to label all the row numbers in a table.
<table>
<thead>
<tr>
<th>Item</th>
<th>Price</th>
</tr>
</thead>
<tbody>
<tr>
<td>Bananas</td>
<td>$2</td>
</tr>
<tr>
<td>Oranges</td>
<td>$8</td>
</tr>
<tr>
<td>Top Sirloin</td>
<td>$20</td>
</tr>
</tbody>
<tfoot>
<tr>
<td>Total</td>
<td>$30</td>
</tr>
</tfoot>
</table>const rows = document.querySelectorAll("tr");
rows.forEach((row) => {
const z = document.createElement("td");
z.textContent = `(row #${row.rowIndex})`;
row.appendChild(z);
});