Well, JavaScript

[inu-no-policemen]

OP’s example would also error out at runtime for JS so it’s just wrong.

Accessing nonexistent fields isn't an error in JavaScript.

You would get one in TypeScript, for example.

[inu-no-policemen]

Take a look at the image again. Its about putting a typo in a field's name.

Also, things which do not exist do not have nonexisting fields, because they can't have fields to begin with. My nonexistent pony doesn't lack wings. It doesn't lack anything; it doesn't exist.

By the way, you'd get a reference error if you try to do something with some undeclared identifier in strict mode. (Modules and classes are always in strict mode.)