javascript check whether a specific element (iframe) exist, if not, appendchild
<p>i want to achieve some feature like this: </p>

<pre><code>var el = document.createElement("iframe");
el.setAttribute('id', 'ifrm');
document.body.appendChild(el);
el.setAttribute('src', 'http://www.example.com');
</code></pre>

<p>and if  "ifrm" exists, jt won't create new iframe. if it doesn't exist, it will create that frame. i want to do this to avoid duplicate frame creation when user keeps click on the same button to generate frame.  is there a way to check whether a specific iframe exists? thanks</p>
