Can Custom Element names contain Unicode?

Question

Surprisingly can't find this on google...

Can the name of a custom element (a la the Web Components set of W3C specs) contain unicode?

This HTML 5 Custom element names? says that a custom element name must begin with an ASCII character, contain a hyphen, and ANY OTHER characters. Does that mean unicode?

Answer 1

TL;DR This great article explains what characters are permitted in javascript. Unfortunately, those won’t work as expected with elements. At least, at the moment.

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The reason is that document.registerElement which is being called on newly created custom elements, will fail:

var a = document.registerElement('a-ℵ');
//⇒ Uncaught SyntaxError: Failed to execute 
//    'registerElement' on 'Document': 
//    Registration failed for type 'a-ℵ'. 
//    The type name is invalid.

That’s because registerElement tries to create internal constructor, different from generic function HTMLElement()/function HTMLUnknownElement() for registered elements:

console.log(document.registerElement('a-b'));
//⇒ function a-b() { [native code] }

I would suggest the internals of browsers are not yet ready for:

//⇒ function a-ℵ() { [native code] }

though you might easily specify:

var ℵ = function() { console.log('IT WORKS') };
ℵ();
//⇒ IT WORKS

I understand this is not exactly an answer you expected, but I hope it sheds some light.