Scripting IFrames in IE and Firefox

Update: Found out Safari requires iframeEl.contentWindow, iframeEl.contentDocument.defaultView doesn't work (or, at least, it doesn't work any more). Turns out that this works for Firefox as well. I've left the other branch for backwards compatibility and also because it is more standard.

Here's how to get a reference to an iframe with JavaScript, in Firefox and IE, IE and Safari:

        var iframeEl = document.getElementById("iframeId");
        var iframeDoc = iframeEl.contentDocument
        var iframeWin;
        if (iframeDoc) { // Firefox
            iframeWin = iframeDoc.defaultView
        } else { // IE
            iframeWin = iframeEl.contentWindow
        }
        if (iframeEl.contentWindow) { // IE and Safari require, but works for Firefox too
            iframeWin = iframeEl.contentWindow;
        } else if (iframeEl.contentDocument) { // Works for Firefox, DOM level 2 standard
            iframeWin = iframeEl.contentDocument.defaultView;
        }

And then you can use iframeWin to get access to JavaScript objects and the DOM of the iframe.

Also, I learned that getElementById() in IE (version 7 tested) picks up elements by name attribute as well, so names and ids need to be unique for all elements on a page for IE.