Question

How would I pass a variable to an iframe which is on the same domain.

The most logical way I can think of would be to use a session variable or cookie?

To put this in context it is the category of a wordpress page.

Answer 1

You can access the parent window using the parent keyword in javascript

Example:

var newValue = parent.getElementById('inputValue').value;

accessing the child window is also possible

var iframeElement = document.getElementById("MyFrame");

var ifram = (iframeElement.contentWindow) ? iframeElement.contentWindow : (iframeElement.contentDocument.document) ? iframeElement.contentDocument.document : iframeElement.contentDocument;