Remember, cross site access to iFrame properties is not possible (security).
<script>
setTimeout(function() {
var iframe = document.getElementById('myframe1');
var innerDoc = (iframe.contentDocument) ? iframe.contentDocument : iframe.contentWindow.document;
var x = innerDoc.getElementsByClassName("place-name");
x[0].innerHTML = "Hello World!";
},5000);
</script>
myvar = document.createElement('input');
myvar.setAttribute('name', 'somename');
myvar.setAttribute('type', 'hidden');
myvar.setAttribute('value', 'somevalue');
form.appendChild(myvar);