[ruslan_mart]

<form>
    <input name="count" type="number" value="5">
    <input onclick="generateBlocks(this.form.elements.count.value)" type="button" value="OK">
</form>

function generateBlocks(count) {
   var fragment = document.createDocumentFragment();

   for(var div, i = 0; i < +count; i++) {
      div = document.createElement('div');
      div.innerHTML = 'DIV #' + (i + 1);
      fragment.appendChild(div);
   }

   document.body.appendChild(fragment);
}