This chapter covers
- The benefits of using enums
- The syntax for numeric and string enums
- What generic types are for
- How to write classes, interfaces, and functions that support generics
In chapter 2, we introduced unions, which allow you to create a custom type by combining several existing types. In this chapter, you’ll learn how to use enums—a way to create a new type based on a limited set of values.
We’ll also introduce generics, which allow you to place type constraints on class members, function parameters, or their return types.
Enumerations (a.k.a. enums) allow you to create limited sets of named constants that have something in common. Such constants can be numbers or strings.
A week has seven days, and you can assign the numbers 1 to 7 to represent them. But what’s the first day of the week?