Re: [w3c/webcomponents] Better custom event support for custom elements would be great (#546)

> Since attributes are notified as soon as the element is upgraded,

Not true, if attributes exist on the element before they are upgraded,
Chrome doesn't call your attributChangedCallback (I guess technically, the
attribute didn't change after the instance was made).

On Sep 16, 2016 4:09 AM, "Andrea Giammarchi" <notifications@github.com>
wrote:

> @chris-morgan <https://github.com/chris-morgan> you could have a simple
> convention like:
>
> class MyImage extends HTMLElement {
>
>   static get observedAttributes() {
>     return ['onerror', 'onload'];
>   }
>
>   attributeChangedCallback(name, oldValue, newValue) {
>     if (/^on/.test(name)) {
>       if (newValue) {
>         this[name] = newValue;
>         this.addEventListener(name.slice(2), this);
>       } else {
>         delete this[name];
>         this.removeEventListener(name.slice(2), this);
>       }
>     } else {
>       // every other attribute logic
>     }
>   }
>
>   // any event previously registered through the instance
>   // will pass through this listener
>   handleEvent(e) {
>     return this['on' + e.type](e);
>   }
>
> }
>
> Since attributes are notified as soon as the element is upgraded, you'll
> have your events and, whenever such attribute will be removed, or changed,
> you'll have them reflected.
>
> The good part of using the instance as listener is that you'll never end
> up with double listeners or never removed one (like unhanded bound events
> would be) so it's quite easy to circumvent the current limit when it comes
> to custom attributes, keeping the on prefix like the de-fact standard to
> define an event.
>
> —
> You are receiving this because you commented.
> Reply to this email directly, view it on GitHub
> <https://github.com/w3c/webcomponents/issues/546#issuecomment-247059876>,
> or mute the thread
> <https://github.com/notifications/unsubscribe-auth/AASKzlnIMXZbTc8RGvWWXWb26eBj5T6Oks5qqBgmgaJpZM4Jjlhf>
> .
>


-- 
You are receiving this because you are subscribed to this thread.
Reply to this email directly or view it on GitHub:
https://github.com/w3c/webcomponents/issues/546#issuecomment-247814904