1. Primitives

JavaScript has three very commonly used primitives: string, number, and boolean. Each has a corresponding type in TypeScript. As you might expect, these are the same names you'd see if you used the JavaScript typeof operator on a value of those types:

• string represents string values like "Hello, world"

• number is for numbers like 42. JavaScript does not have a special runtime value for integers, so there's no equivalent to int or float - everything is simply number

• boolean is for the two values true and false

The type names String, Number, and Boolean (starting with capital letters) are legal, but refer to some special built-in types that will very rarely appear in your code. Always use string, number, or boolean for types.

— The TypeScript Handbook: Everyday Types

Exercises

• Ex. 1.1: string
• Ex. 1.2: number
• Ex. 1.3: boolean