Primitive types

TypeScriptJunior~1 min read

TypeScript has several primitive types, which are the basic building blocks of the language (that is, not objects and with no methods except the built-in ones via the prototype). Here is the full list:

Main primitive types

string - a string Used for text data.

javascript

let name: string = "Tim";

number - a number Covers both integer and fractional values (all numbers are floating-point).

javascript

let age: number = 25;
let price: number = 19.99;

boolean - a boolean value (true/false)

javascript

let isOnline: boolean = true;

bigint - an integer of arbitrary length (ES2020+) Used when you need to work with very large numbers.

javascript

let big: bigint = 123456789012345678901234567890n;

symbol - a unique identifier (ES2015+) Guarantees the uniqueness of a value, often used as an object key.

javascript

const id: symbol = Symbol("id");

undefined - the "not defined" value Usually means that a variable is declared but has no value.

javascript

let value: undefined = undefined;

null - the intentional absence of a value

javascript

let empty: null = null;

void - "returns nothing" Used as the type of a function that returns no value.

javascript

function logMessage(): void {
  console.log("Hello");
}

never - "never happens" Used for functions that never complete successfully (for example, they throw an error or loop forever).

javascript

function fail(): never {
  throw new Error("Error!");
}

unknown - an "unknown type" A safe alternative to any. Requires a check before use.

javascript

let data: unknown = "Hello";
if (typeof data === "string") {
  console.log(data.toUpperCase());
}

any - "any type" Turns off type checking (used rarely and carefully).

javascript

let something: any = 123;
something = "text"; // allowed

Summary:

Category	Types
Primitive	`string`, `number`, `boolean`, `bigint`, `symbol`, `null`, `undefined`
Special utility	`void`, `never`, `unknown`, `any`

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Primitive types

#Main primitive types

#Special (not quite primitive, but closely related)

#Summary:

Short Answer

Main primitive types

Special (not quite primitive, but closely related)

Summary: