[javascript] Create <div> and append <div> dynamically

I am trying to create a <div> dynamically, with an appended <div> inside. I have this so far which works:

var iDiv = document.createElement('div');
iDiv.id = 'block';
iDiv.className = 'block';
document.getElementsByTagName('body')[0].appendChild(iDiv);

I am just having trouble creating and appending the second div to the first div.

I essentially want to do this as the final markup:

<div id="block" class="block">
   <div class="block-2"></div>
</div>

    while(i<10){
               $('#Postsoutput').prepend('<div id="first'+i+'">'+i+'</div>');
               /* get the dynamic Div*/
               $('#first'+i).hide(1000);
               $('#first'+i).show(1000);
                i++;
                }

var iDiv = document.createElement('div');
iDiv.id = 'block';
iDiv.className = 'block';

var iDiv2 = document.createElement('div');
iDiv2.className = "block-2";

iDiv.appendChild(iDiv2);
// Append to the document last so that the first append is more efficient.
document.body.appendChild(iDiv);

Well, I don't know how dynamic this is is, but sometimes this might save your debugging life:

var daString="<div id=\'block\' class=\'block\'><div class=\'block-2\'></div></div>";
var daParent=document.getElementById("the ID of whatever your parent is goes in here");
daParent.innerHTML=daString;

"Rat javascript" If I did it correctly. Works for me directly when the div and contents are not themselves dynamic of course, or you can even manipulate the string to change that too, though the string manipulating is complex than the "element.property=bla" approach, this gives some very welcome flexibility, and is a great debugging tool too :) Hope it helps.

var i=0,length=2;

     for(i; i<=length;i++)
 {
  $('#footer-div'+[i]).append($('<div class="ui-footer ui-bar-b ui-footer-fixed slideup" data-theme="b" data-position="fixed" data-role="footer" role="contentinfo" ><h3 class="ui-title" role="heading" aria-level="1">Advertisement </h3></div>')); 

 }

var arrayDiv = new Array();
    for(var i=0; i <= 1; i++){
        arrayDiv[i] = document.createElement('div');
        arrayDiv[i].id = 'block' + i;
        arrayDiv[i].className = 'block' + i;
    }
    document.body.appendChild(arrayDiv[0].appendChild(arrayDiv[1]));

var iDiv = document.createElement('div');

iDiv.id = 'block';
iDiv.className = 'block';
document.getElementsByTagName('body')[0].appendChild(iDiv);

var div2 = document.createElement('div');

div2.className = 'block-2';
iDiv.appendChild(div2);

window.onload = function() {
  var iDiv = document.createElement('div');
  iDiv.id = 'block';
  iDiv.className = 'block';
  document.body.appendChild(iDiv);

  var iiDiv = document.createElement('div');
  iiDiv.className = 'block-2';

  var s = document.getElementById('block');
  s.appendChild(iiDiv);
}

var iDiv = document.createElement('div'),
    jDiv = document.createElement('div');
iDiv.id = 'block';
iDiv.className = 'block';
jDiv.className = 'block-2';
iDiv.appendChild(jDiv);
document.getElementsByTagName('body')[0].appendChild(iDiv);