title: Why is insertBefore not working?
body: <p>I have written the code shown below. I am trying to position the element "h45" above the "age". Somehow, it does not work and I get the following error : "The new child element contains the parent." Does anybody know why this happens and how I could fix it? I am new to JavaScript and I dont understand what I am doing wrong. Thank you all in advance!`</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>var lastName=document.getElementById("lastName");
   var firstName=document.getElementById("firstName");
   var age= document.getElementById("alter")
   age.addEventListener("blur",showage,false);
  
  function showage()
      {
          if (/[^0-9]/.test(age.value)) {
              
                var h45 = document.createElement("h4");
                var txttt = document.createTextNode("Bitte geben Sie nur Nummern ein");
                h45.appendChild(txttt);
                age.parentNode.appendChild(h45);
                h45.insertBefore(h45,age);
                h45.style.color = "red";
         
              return false;
          }
          else {
              return true;
          }
      }</code></pre>
  </div>
  </div>
  </p>