JSFiddle - React, Tailwind, and code Playground

HTML

<input type="button" name="button" id="button" value="Add Row" onClick="addRow();">
<table cellspacing="0" cellpadding="0" id="tbl" border=1>
  <tr>
    <th scope="col">Col 1</th>
    <th scope="col">Col 2</th>
  </tr>
  <tr>
    <td>Dummy </td>
    <td>Dummy</td>
  </tr>
</table>

JavaScript

function addRow() {
	var td, tx;
	var tbl = document.getElementById("tbl");
	var tr = document.createElement("tr");
	for(var x=0; x<2; x++ ) {
		td = document.createElement("td");
		tx = document.createTextNode(".");
		td.appendChild( tx );
		tr.appendChild( td );
	}
	tbl.appendChild( tr );
}