Check if NodeFilter.length is defined correctly.

[Ms2ger]

Check if NodeFilter.length is defined correctly.

[bzbarsky]

The spec seems to only define a "length" property for non-callback interfaces, implying that there is no such property on the NodeFilter object. So doing NodeFilter.length will return Function.prototype.length, which is 0.

That said, NodeFilter.hasOwnProperty("length") actually returns true in both Gecko and Blink.

[Ms2ger]

I'm not sure where Function.prototype.length comes from, given

Remember that interface objects for callback interfaces only exist if they have constants declared on them; when they do exist, they are not function objects.

[bzbarsky]

Oh. Well, NodeFilter.__proto__ == Function.prototype is true in both Gecko and Blink. Yes, that's not what IDL says right now. It's not clear to me why IDL says what it does and which should change.

[nox]

@bzbarsky That condition is false in Safari.

[nox]

Mentioning #78 because NodeFilter is the only legacy callback interface we have.

[bzbarsky]

@nox What is it in IE? Seems to me like we should do the simplest thing that requires the fewest UAs to change.

[nox]

@bzbarsky No idea, I don't have any Windows box. :(

[domenic]

NodeFilter.__proto__ === Function.prototype in latest Edge.

[ArkadiuszMichalski]

Hmm, more results for:

<script>
    console.log(NodeFilter.__proto__ == Function.prototype);
    console.log(typeof NodeFilter);
    console.log(NodeFilter.length);
    console.log(NodeFilter.hasOwnProperty("length"));
</script>

IE11: false, object, undefined, false
Opera 12.x: true, function, 0, false
Firefox and Chrome: true, function, 0, true

[arronei]

Edge: true, function, 0, false (length is a known Edge bug and should be true)