That doesn't really make things immutable. Even ignoring the deep vs shallow issue, consider what effect Object.freeze has on a JS Map (hint: none, really; you can still add/remove things).

Right, that's where libraries like ImmutableJS come in.

That's not deeply immutable like you'd want for sharing objects across threads, or even for using in contexts like React and Redux.

Not too hard to call Object.freeze() recursively to get the deep immutability you need. And of course there's ImmutableJS for other immutable data structures.