Issue with "Optional chaining (?.)": …

[davidecarpini]

MDN URL: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining

What information was incorrect, unhelpful, or incomplete?

this information is not totally true, or mind-tricky:
Optional chaining cannot be used on a non-existent root object. It does not replace checks like if (typeof a == "undefined").

expected:

Optional chaining cannot be used on a non-declared root object, but can be used with undefined root object

after tested:

[sideshowbarker]

Thanks much — I’ve opened #1413 with a patch that updates that article.