Need help with simple Javascript Timer

I want this to start running as soon as this page is loaded. It is for a Drupal site (a CMS), so I do not want to add a 'onload' to the body tag. I also don't want to alter the header text (which will permanently load to every page from now on). I just want to do this locally within the HTML.



This doesn't work; I think it is obvious what I am trying to do; it's just a timer:

<h1 id="header">Old Header</h1>

<script type="text/javascript">
  document.getElementById("header").innerHTML=0;
  var t;
  var c = 1;
  while(true){
     document.getElementById('header').inerHTML=c;
     c=c+1;
     timedCount(1000);
                                    //t=setTimeout("timedCount()",1000);   <--if I replace the above line with this; it does not work either.
}  
</script>

Code (markup):

 

document.getElementById('header').inerHTML=c; <---

 

Try this,

<h1 id="header">Old Header</h1>

<script type="text/javascript">
  document.getElementById("header").innerHTML=0;
  var t;
  var c = 1;
  
  function timedCount() {
 
     document.getElementById('header').innerHTML=c;
     c=c+1;
     t=setTimeout(timedCount,1000);
  }

  timedCount(); 
</script>

Code (markup):