Common TypeScript Types: Primitives, Arrays, Tuples, Enums, and Literals

TypeScript's type system lets us describe data more clearly. Common categories include primitive types, arrays, tuples, enums, union types, and literal types.

Primitive Types

let title: string = "TypeScript";
let count: number = 10;
let enabled: boolean = true;
let big: bigint = 9007199254740991n;

string represents text, number represents both integers and floating-point numbers, and boolean represents true or false values.

Arrays

Arrays can be declared in two common ways.

let numbers: number[] = [1, 2, 3];
let names: Array<string> = ["Alice", "Bob"];

When elements should share a type, make that element type explicit.

Tuples

Tuples describe fixed-position data.

let user: [string, number] = ["Alice", 25];
let option: [string, boolean?] = ["dark"];
let list: [number, ...string[]] = [1, "a", "b"];

Enums

Enums define named constants.

enum Color {
  Red,
  Green,
  Blue,
}
 
const favorite: Color = Color.Green;

In many projects, union literals are also a practical alternative.

type Direction = "up" | "down" | "left" | "right";

Union Types

Union types allow a value to be one of several types.

let id: string | number;
id = "u_1";
id = 1001;

They are useful for API parameters, form inputs, and state values.

Literal Types

Literal types restrict values to exact options.

type Gender = "male" | "female";
type Status = "idle" | "loading" | "success" | "error";

This makes state modeling safer and avoids many magic-string mistakes.

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