Errors when extending HTMLElement or Event classes

[web-padawan]

I'm getting the following error when attempting to extend built-in classes.

Cannot use 'in' operator to search for 'start' in undefined

The following examples produce the error:

// error
class MyElement extends HTMLElement {
}

// error
class MyEvent extends Event {
}

I also tried class MyArray extends Array and it worked.

[JSMonk]

Hi @web-padawan. Currently, the browser environment still in development. We try to implement it as soon as possible. Thank you for the issue and your interest in the project ^_^