Mastering TypeScript: Advanced Types and Techniques

TypeScript is a powerful superset of JavaScript that adds optional static typing and other features. In this post, we'll explore some of the more advanced types and techniques that TypeScript offers.

Union Types: Union types allow a value to be one of several types. For example:

let result: number | string;
result = 10; // OK
result = "hello"; // Also OK

Conditional Types: Conditional types select one of two possible types based on a condition:

type CheckNumber<T> = T extends number ? "Is a number" : "Not a number";
type Result = CheckNumber<5>; // "Is a number"

Mapped Types: Mapped types allow you to create new types based on old ones:

type Readonly<T> = {
  readonly [P in keyof T]: T[P];
};

type Person = { name: string; age: number };
type ReadonlyPerson = Readonly<Person>;

Utility Types: TypeScript provides several utility types to facilitate common type transformations:

type Partial<T> = { [P in keyof T]?: T[P] };
type Required<T> = { [P in keyof T]-?: T[P] };
type Pick<T, K extends keyof T> = { [P in K]: T[P] };

By mastering these advanced TypeScript features, you can write more robust and maintainable code, catching more errors at compile-time and improving your overall development experience.