Create <tr> in table without ID using JavaScript

Question

I have a question about dynamical row creating to existing HTML table. I am sorry, if question seems stupid, but I am beginner at JavaScript. Here is HTML table (I cannot change any HTML code here):

I have to add rows with JavaScript, but because I cannot add table id to HTML code, it's impossible to do it by insertRow() function. I have tried with this code, but it doesn't work (not even with getElementsByClassName('some-tab')). The rows are not created. Code:

var something = getElementsByTagName('table');
var tableca = something[0];

for (var i = 1; i < 4; i++) {

  var tr = document.createElement('tr');

  var td1 = document.createElement('td');
  var td2 = document.createElement('td');

  var text1 = document.createTextNode('Text1');
  var text2 = document.createTextNode('Text2');

  td1.appendChild(text1);
  td2.appendChild(text2);
  tr.appendChild(td1);
  tr.appendChild(td2);

  tableca.appendChild(tr);
}
document.body.appendChild(tableca);

<table class="some-tab">
  <tr>
    <th>Name</th>
    <th>Description</th>
  </tr>
  <tr>
    <td id="Username">Admin</td>
    <td id="Description">STH STH STH!</td>
  </tr>
</table>

Can anyone help me, please? Thank you very much! :D

Answer 1

Look at your browser's developer tools.

Uncaught ReferenceError: getElementsByTagName is not defined

getElementsByTagName is a method of the document object and of DOM element objects. It isn't a global.

Just edit the first line of your code.

var something = document.getElementsByTagName('table');
var tableca = something[0];

for (var i = 1; i < 4; i++) {

  var tr = document.createElement('tr');

  var td1 = document.createElement('td');
  var td2 = document.createElement('td');

  var text1 = document.createTextNode('Text1');
  var text2 = document.createTextNode('Text2');

  td1.appendChild(text1);
  td2.appendChild(text2);
  tr.appendChild(td1);
  tr.appendChild(td2);

  tableca.appendChild(tr);
}
document.body.appendChild(tableca);

<table class="some-tab">
  <tr>
    <th>Name</th>
    <th>Description</th>
  </tr>
  <tr>
    <td id="Username">Admin</td>
    <td id="Description">STH STH STH!</td>
  </tr>
</table>