JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://ajax.googleapis.com/ajax/libs/jqueryui/1.8.4/themes/ui-lightness/jquery-ui.css">
<table>
 <tr>
   <td>col 1</td><td>col2</td>
 </tr>
 <tr id="insert">
   <td>field</td><td>Field 2</td>
 </tr>
 <tr>
   <td>another field</td><td>one more field</td>
 </tr>
</table>

JavaScript

var new_row = document.createElement('tr');
new_row.insertCell(0).innerHTML = "test";
new_row.insertCell(1).innerHTML = "test2";
insertAfter(document.getElementById("insert"), new_row);


function insertAfter(target, el) {
    if( !target.nextSibling )
        target.parentNode.appendChild( el );
    else
        target.parentNode.insertBefore( el, target.nextSibling );
};