Bug 74193 – typeof Node should be function

• Component: DOM
• Status: RESOLVED DUPLICATE

[Erik Arvidsson]

https://www.w3.org/Bugs/Public/show_bug.cgi?id=12458

Related:

Node instanceof Function // should be true
Function.prototype.isPrototypeOf(Node)  // should be true

typeof Object.getPrototypeOf(Node)  // should be "function"

[Oliver Hunt]

Node is a constructor, not a function.

ES spec is fairly clear on this -- typeof x === "function" only if x is directly callable.

If the webidl spec now calls for element constructors to be callable directly (instead of via new) then the bug here is that NodeConstructor isn't a function, not any of the other things you're claiming.

[Erik Arvidsson]

ES6 classes have a [[Call]] but it throws immediately.

http://people.mozilla.org/~jorendorff/es6-draft.html#sec-ecmascript-function-objects-call-thisargument-argumentslist

2. If F’s [[FunctionKind]] internal slot is "classConstructor", throw a TypeError exception.


For WebIDL all constructors have a [[Call]]. It used to do the same thing as [[Construct]], which was to throw if non constructable. There is an open WebIDL bug to throw on [[Call]], See https://www.w3.org/Bugs/Public/show_bug.cgi?id=22808, and Firefox just made that change too.

[Joe Pea]

Can you guys please fix this? The reason for following the spec in such a way doesn't outweight the benefit of being able extend from HTMLElement, especially when using the new Custom Element API.

After applying a `document.registerElement` polyfill in Safari, this is what we have to do in order to make a Custom Element that extends from HTMLElement using ES6 classes:


```js
import 'document-register-element' // polyfill

// hack for Safari.
if (typeof window.HTMLElement != 'function') {
    const _HTMLElement = function HTMLElement(){}
    _HTMLElement.prototype = window.HTMLElement.prototype
    window.HTMLElement = _HTMLElement
}

class MyElement extends window.HTMLElement {
    createdCallback() { ... }
    attachedCallback() { ... }
    detachedCallback() { ... }
    attributeChangedCallback(attribute, oldValue, newValue) { ... }
}
MyElement = document.registerElement('motor-node', MyElement)

export default MyElement
```

I think it's time to fix this and get Custom Elements working, and in general to be compatible with ES6 classes.

[Chris Dumez]

This has already been fixed a while back via Bug 154038. You can give it a try in the Safari Technology Preview (all your 3 tests pass there).

*** This bug has been marked as a duplicate of bug 154038 ***