Re: Why can't we just use constructor instead of createdCallback?

On Dec 5, 2013, at 8:43 PM, Dimitri Glazkov <dglazkov@chromium.org> wrote:
> There were several threads around this in March/April, but the main gist is that we can't allow running user code when the parser is building the tree, and thus we would need to decouple the timing of the constructor being called from the [[Construct]] internal method to make constructors workable.

That sounds like an implementation detail of Blink/WebKit.  Also, JS "wrappers" aren't even constructed immediately for builtin elements in WebKit and Blink so delaying the construction of elements until later time (e.g. end of micro task) seems fine.

> But then they aren't constructors, but callbacks, since the object would already be exist (and be in a tree). So we decided to not lie and just call them callbacks, rather than constructors.

It would be extremely unfortunate if authors can't use constructor() in the world we have ES6 classes.

class MyButtonElement extends HTMLElement {
    constructor() {
        ...
    }
}

looks much more natural than

class MyButtonElement extends HTMLElement {
    constructor() {
        // Would I ever be called? If so, when?  Is that safe?
    }
    createdCallback() {
        ...
    }
}

> http://lists.w3.org/Archives/Public/public-webapps/2013JanMar/0728.html
> http://lists.w3.org/Archives/Public/public-webapps/2013AprJun/thread.html#msg152
> I am probably forgetting some…

Thanks for the pointers again.

- R. Niwa