How to find out if DOMContentLoaded event comes from iframe or not?

I am working on a Firefox extension and it uses something like this:

function myExt()
{
    this.handleEvent = function (event)
    {
        switch (event.type)
        {
            case "DOMContentLoaded":
            {
                alert('fired');
            }
        }
    }

    window.addEventListener ("DOMContentLoaded", this, false);
}

My problem is that the alert gets executed multiple times if the page contents iframes, so what I am looking to do is, using "event" on this.handleEvent I need to find out if event.target references the top window or the iframe window.

How c开发者_Python百科an I do this?

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You could try checking for event.target.frameElement. If it's undefined then it's the main document, but if it is defined then it's a frame. I can't remember if this is only for frames, though, or if it's for iframes too.

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Yeah, iframe is weird in that will fire DOMContentLoaded. It treats the content as if it were in its own 'window'. Have you tried getting the event.target's parent or ownerDocument?

I used Firebug on an SVG loaded into an <object> tag and I believe that ownerDocument gets what you're looking for.

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I am still doing some tests but it looks like this function does the job:

this.isTopLevel = function(event){
    var doc = event.target;
    for(var i = 0; i < gBrowser.browsers.length; i++) {
        if(gBrowser.browsers[i].contentDocument == doc) return true;
    }
    return false;
};

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I'm using this snippet to filter out iframes:

var browser = gBrowser.getBrowserForDocument(event.target);
var pageIsFrame = (event.target instanceof Ci.nsIDOMHTMLDocument &&
  event.target != browser.contentDocument);
if (pageIsFrame) {
  // Not interested in frames.
  return;
}

You need Chrome privileges for that.

In the new add-on SDK content scripts (where you don't have Chrome privileges), I'm using this:

if (window.frameElement) {
  // This is an iframe.
  //...
}

(See MDC doc here or here).