title: TypeError: table is null when adding row to table
body: <p>I am Trying to create and add elements to a table. </p>
  
  <pre><code>function flaeche() {
      let tableID = "testTable";
      let x = document.createElement("TABLE");
      x.setAttribute("id", tableID);
      for (let argument of arguments) {
          let radius = ((argument*argument)*Math.PI).toFixed(2);
          addRow(argument,radius,tableID);
      }
  }
  
  function addRow(value, result, tableID){
      let table = document.getElementById(tableID);
      let row = table.insertRow(0);
      let cell1 = row.insertCell(0);
      let cell2 = row.insertCell(1);
      cell1.innerHTML = value;
      cell2.innerHTML = result;
  }
  </code></pre>
  
  <p>If I try to run the code I get the following error: 
  <code>TypeError: table is null</code> at <code>addRow line 30:5</code> 
  which corresponds to 
  <code>let table = document.getElementById(tableID);</code>
  I really have no idea why it says so since I am fairly new to JavaScript. I appreciate your help.</p>