Creating element in place

I want to create an element in place where javascript function run.

<script>
var uni开发者_开发问答qid='an unique Id';
document.write('<iframe id='+uniqid+'></iframe>');
someAsyncFunction(callback)
</script>

in other part of code I set additional parameters for this element

<script>
callback=function(paramfromcallback){
    getElementById(uniqid).url=paramfromcallback;
}
</script>

but this is not work in IE. I can't find this element.

My problem is:

1. There are many elements on page, for each element must be set only this element parameters

2. I do not know which element is parent, I do not know the script element ID. I need insert an element in place where are first script called

3. First part of code executed before any call back, and I want to keep it asynchronous

Depending on the order your script blocks are hit, you could have a number of issues here. document.write() creates interesting problems with inline script. More often than not, any script that comes after it won't be able to use the results of the doc.write until after the page finishes loading -- or from within another document.write() block. Waiting for the window to be fully loaded could solve your issue. How about something like this -

Defined Once:

function callback(id) {
  var el = document.getElementById(id);
  if (el !== null) {
    el.url = 'http://google.com';
  }
}

Then anywhere you want to write out an iframe:

(function(){
  var id = 'an_unique_Id';
  document.write('<iframe id='+id+'></iframe>');

  var l = window.onload;
  var n = function() { someAsyncFunction(function() { callback(id); }); };

   window.onload = (typeof l == 'function') ? function() { l(); n(); } : n;
})();

First, use:

document.getElementById(uniqid).url = 'http://google.com';

The method is part of the document object, so you can only use it by prepending document.

Second, use:

var callback = function() {

Will not break your code probably, but variables should be declared with var