Knowing if a previous handler for an event returned false. defaultPrevented in IE < 9?

Question

I've put a global modal "Loading, please wait" <div> in an application. It is showing every time an <a> or <input type="button"> is clicked. This is achieved by assigning the <body> an onclick event handler in onload, so that it gets executed when the event bubbles up:

<body onload="setup()">
    <!-- No control over what will be here -->
</body>

<script>
function setup() {
    document.getElementsByTagName('body')[0].onclick = clickFunc;
}
function clickFunc(eventData) {
    var clickedElement = (window.event) ? event.srcElement : eventData.target;
    if (someConditions) { 
        document.getElementById('modal').style.display = "block";
    }
}
</script>

Now, I've got some components in the markup (over which I have no control) that do return false in their onclicks. That's causing the modal popup to show and just stay there when there's a confirm() and the user denies. Probably the proper way of dealing with this would have been preventDefault(), so that the event wouldn't bubble up, as explained in event.preventDefault() vs. return false.

But I don't have control over that part, so: Is there a way (preferrably non-jquery+cross-browser) to know the result of previous executions of the event handler (at lower levels) ?

If there isn't I guess I'll just have to refrain from showing the modal <div> whenever the component's onclick contains return false.

Here is a JSFiddle for testing.

UPDATE

Bergi's answer below is what I was searching for. However, defaultPrevented doesn't seem to be supported in IE < 9. Is there an equivalent/workaround to achieve that in IE < 9?

Is there any common pattern on your clickable elements to recognize them, or any common patter on the clickable elements over which you don't have control? — Áxel Costas Pena, Sep 28 '12 at 14:00
There's no other pattern to look for besides `clickedElement.onclick.toString().indexOf('return false') != -1`. — Xavi López, Sep 28 '12 at 14:12
Sadly, this isn't very recommended, bacause function decompilation is not a requirement of a valid ECMAScript implementation, I mean, a browser is not required by the standards to give you the string-conversion of a function when you do somefunction.toString()... All I can think is looking at event.target, if nodeName is not "A", look at parentNode, parentNode, parentNode, etc, until its nodeName is "A", then check if onclick is null, or until you reach the body. But if you want to use onclick in your own link elements this won't work... Any other tip to help us help you? ;) — Áxel Costas Pena, Sep 28 '12 at 14:43
Thanks for your comments, @Áxel. In `someConditions` I'm already looking up the hierarchy from the event's target to look for ``s . The problem is just with elements that can `return false` in their `onclick` event handlers. I'd rather know if they returned false in order not to show the dialog if they did. I still want to show the popup if there's an `onclick` that doesn't return `false`. [@Bergi's suggestion](http://stackoverflow.com/a/12641399/851811) is what I was looking for. However, IE < 9 doesn't seem to support `defaultPrevented`. — Xavi López, Sep 28 '12 at 14:52

Bergi · Accepted Answer · 2012-09-28T14:12:22.980

1

You could check for (window.event ? event.defaultPrevented : eventData.isDefaultPrevented()) == false to catch propagated events that have not returned false.

edited Sep 28 '12 at 14:12

answered Sep 28 '12 at 13:54

Bergi

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Thanks for your answer. I've tried it in a [fiddle](http://jsfiddle.net/wTzu7/3/), but `isDefaultPrevented` (which doesn't seem to be a function, by the way) is always `undefined`. Also, thanks for telling me about `defaultPrevented` :) – Xavi López Sep 28 '12 at 14:09
1

Uh, boo to non-W3-standard browsers (you know which I mean) - [fixed fiddle](http://jsfiddle.net/xaSb5/) – Bergi Sep 28 '12 at 14:14
Curiously enough, it doesn't work for **that** browser (IE7 here). Also tried `returnValue` as explained [here](http://stackoverflow.com/q/1000597/851811) but the value doesn't seem to be available once it has bubbled up. – Xavi López Sep 28 '12 at 14:31
Seems like `defaultPrevented` is only supported in [IE9](http://msdn.microsoft.com/en-us/library/ie/ff974943(v=vs.85).aspx). I'll unaccept for the moment in case another answer comes up, but this was the answer I was looking for. – Xavi López Sep 28 '12 at 14:54

Knowing if a previous handler for an event returned false. defaultPrevented in IE < 9?

UPDATE

1 Answers1

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