Method for iframe parent page to get child page parameters

1. Iframe in the parent page

 
<iframe name="parentPage"></iframe> 

2. Attributes of elements in child pages

 
<input type="text" id="date" data-dojo-type="dijit/form/DateTextBox" value="2013-11-12"/> 

3. Take the median value of DateTextBox in the child page

 
var statisDate = window.frames["parentPage"].document.getElementById('date').value;