TypeScript allows us to decorate specification-compliant ECMAScript with type information that we can analyze and output as plain JavaScript using a dedicated compiler. In large-scale projects, this sort of static analysis can catch potential bugs ahead of resorting to lengthy debugging sessions, let alone deploying to production. However, reference types in TypeScript are still mutable, which can lead to unintended side effects in our software. In this article, we’ll look at possible constructs where prohibiting references from being mutated can…