The primitives: string, number, and boolean These will later form the core building blocks of more complex types. We’ll start by reviewing the most basic and common types you might encounter when writing JavaScript or TypeScript code. Types can also appear in many more places than just type annotations.Īs we learn about the types themselves, we’ll also learn about the places where we can refer to these types to form new constructs. This isn’t an exhaustive list, and future chapters will describe more ways to name and use other types. In this chapter, we’ll cover some of the most common types of values you’ll find in JavaScript code, and explain the corresponding ways to describe those types in TypeScript.