> 3) const + deep Object.freeze() makes for a complete const. The trouble with this approach is that runtime checks are only a guarantee that the code you've _

> 3) const + deep Object.freeze() makes for a complete const. The trouble with this approach is that runtime checks are only a guarantee that the code you've _exercised_ does not break the contract. In that respect, `const` is deeply different than `.freeze`, in the same way that runtime assertions are deeply different than type checking.