JSFiddle - React, Tailwind, and code Playground

HTML

<div>
<table>
<tbody id="tbodyBox1">
    <tr><td><input type=radio /></td><td><input type=text /></td></tr>
    <tr><td><input type=radio /></td><td><input type=text /></td></tr>
    <tr><td>irgendwas</td></tr>
    <tr><td><input type=radio /></td><td><input type=text /></td></tr>
<tr><td>irgendwas</td></tr>
<tr><td>irgendwas</td></tr>
<tr><td>irgendwas</td></tr>
</tbody>
</table>
</div>

JavaScript

var tbodyBox1 = document.getElementById( "tbodyBox1" );
tbodyBox1.addEventListener( "click", box1btnsOnClick );

function box1btnsOnClick( e ) {
  var e = e || window.event;
  var target = e.target || e.srcElement;
  var num = getRow( target ); // num ist dann die Position der <tr> in <tbody>, wo der Click war
  alert('Zeile '+ (num +1) +' geklickt.');
    
  function getRow( elm ) {
    var c = tbodyBox1.children; // die <tr>
    for ( var i = 0; i < c.length; i++ ) {
      var td = c[ i ].firstElementChild; // <td> in <tr>
      var btn = td.firstElementChild; // <input> in <td>

      if ( btn === elm ) {
         return i;
         break;
      }

    }

  }
}