Primitive Types

TypeScript's most basic types map directly onto JavaScript's primitive values: string for text, number for all numbers, and boolean for true/false. Each one is written in lowercase, right after a variable's name.

let username: string = "amara";
let score: number = 87;
let isActive: boolean = true;

number covers every numeric value in TypeScript — whole numbers, decimals, negatives — there's no separate int, float, or double the way there is in some other languages. JavaScript only has one numeric type under the hood, and TypeScript matches that.

let price: number = 19.99;
let temperature: number = -4;
let quantity: number = 12;

string covers any text, written with single quotes, double quotes, or backticks for template literals — TypeScript doesn't care which quoting style you use, only that the value is text.

let city: string = 'Nairobi';
let greeting: string = `Hello, ${city}!`;

let isActive: ____ = true; is the correct annotation for a variable that only ever holds true or false.

Which type would you use to annotate a variable that holds the value 3.14?

TypeScript has separate int and float types for whole numbers and decimals.