JSFiddle - React, Tailwind, and code Playground

HTML

<table id="datatable">
       <tr>
        <td><input type="text"  /></td>
       </tr>
       <tr>
        <td><input type="text"  /></td>
       </tr>
     </table> 

<button type="button" id="add" onclick="addRow('dataTable')">
        <b>Add</b>
 </button>

JavaScript

function addRow(tableID) {
    alert('ttt');
        var table = document.getElementById(tableID);
        var rowCount = table.rows.length;
        var row = table.insertRow(rowCount);
        var colCount = table.rows[0].cells.length;
        for(var i=0; i<colCount; i++) {              
            var newcell = row.insertCell(i);
            newcell.innerHTML = table.rows[0].cells[i].innerHTML;
            //alert(newcell.childNodes);
            switch(newcell.childNodes[0].type) {
            case "text":
            newcell.childNodes[0].value = "";
            break;
            case "checkbox":
            newcell.childNodes[0].checked = false;
            break;
            case "select-one":
            newcell.childNodes[0].selectedIndex = 0;
            break;
            }
        }
        }