[Kailhus]

Yep, I believe you'd need to call Object.seal(foo) to prevent mutability. Haven't really had the chance to use it

[mwcz]

Object.freeze is the one you're looking for.

const + Object.freeze is a lot to remember and cumbersome to use throughout a codebase, very relevant to Carmack's wish for immutability by default. I'm grateful Rust opted for that default.