在YUI中防止键监听器中的默认行为

Question

I have a web page where I'd like to remap Ctrl+N to a different behavior. I followed YUI's example of register Key Listeners and my function is called but Firefox still creates a new browser window. Things seem to work fine on IE7. How do I stop the new window from showing up?

Example:

var kl2 = new YAHOO.util.KeyListener(document, { ctrl:true, keys:78 },
             {fn:function(event) {
                     YAHOO.util.Event.stopEvent(event); // Doesn't help
                     alert('Click');}});
kl2.enable();

It is possible to remove default behavior. Google Docs overrides Ctrl+S to save your document instead of bringing up Firefox's save dialog. I tried the example above with Ctrl+S but Firefox's save dialog still pops up. Since Google can stop the save dialog from coming up I'm sure there's a way to prevent most default keyboard shortcuts.

Answer 1

The trick is the 'fn' function is whack.

Experimentally, you can see that the function type for fn takes two parameters. The first param actually contains the TYPE of event. The second one contains... and this is screwy: an array containing the codepoint at index 0 and the actual event object at index 1.

So changing your code around a bit, it should look like this:

function callback(type, args)
{
    var event = args[1]; // the actual event object
    alert('Click');

    // like stopEvent, but the event still propogates to other YUI handlers
    YAHOO.util.Event.preventDefault(event);
}
var kl2 = new YAHOO.util.KeyListener(document, { ctrl:true, keys:78 }, {fn:callback});
kl2.enable();

Also, for the love of lisp, don't use raw code points in your code. Use 'N'.charCodeAt(0) instead of "78". Or wrap it up as a function

function ord(char)
{
    return char.charCodeAt(0);
}

Answer 2

I'm just guessing here but I don't think it can be done.

If it's possible it definitely shouldn't be. Generic keyboard shortcuts are something you should not mess with. What's next? Hook the window close button to open a new window...

Answer 3

Using YUI's event util, you could try and use the stopEvent method:

However, because most users are used to those keypresses doing a particular thing in the browser (new window in your example), I always avoid clashes, which in effect means I don't use any of the meta or control keys.

I simply use letters, on their own, which is fine until you have text entry boxes, so this bit of advice might be less useful to you.

Answer 4

Although overriding default browser shortcuts is not trivial, in some cases it is worth to do this since it gives a more professional look of the application. Take a look at this script:

http://www.openjs.com/scripts/events/keyboard_shortcuts/index.php#disable_in_input

It turns out to work fine for me..