Would you mind to elaborate? How does "having referential transparency in mind" protect against typical refactoring errors, such as an unexpected "undefined" va

Would you mind to elaborate? How does "having referential transparency in mind" protect against typical refactoring errors, such as an unexpected "undefined" value due to a typo in a field name? (Of course you could argue that you don't need OCaml for that, as TypeScript or Flow can prevent this, too. But then the argument of using "dynamic" JavaScript instead of static types is moot.)