Summary
TypeScript complements JavaScript with a rich type system, and in this chapter, we experienced catching errors early using TypeScript’s type checking.
We also learned that JavaScript types, such as number and string, can be used in TypeScript, as well as types that only exist in TypeScript, such as Date and unknown.
We explored union types and learned that these are great for representing a specific set of strings. We now understand that string enumerations are an alternative to string union types if the string values aren’t very meaningful.
New types can be created using type aliases. We learned that type aliases could be based on objects, functions, or even union types. We now know that the ? symbol in a type annotation makes an object property or function parameter optional.
We also learned a fair bit about the TypeScript compiler and how it can work well in different use cases because it is very configurable. This will be important when we start...
