Further upgrade of custom elements

[thepian]

I have a particular use case that made me wonder if there should be a method for upgrading a single element to a custom class. Like define, but for a specific element, so customElements.upgrade(el,class). I know that WebKit doesn't want to support upgrading builtin elements, but I'm thinking about custom elements.

The use case is the use of custom elements in <template>s where the rendered custom element relies on a link to the source custom element within the template. The element in the template provides extra functionality.

I suppose this can be done simply by changing the constructor or __proto__ of the element, but I'm unaware if that is supported on all browsers. In that case I guess this is not worth adding to the API.

[annevk]

All browsers support __proto__. It's not a great way to write code though I believe.

[rniwa]

It's standardized in ECMA2015+. You can also use the newly added Object.setPrototypeOf.