Advanced TypeScript Patterns for Modern Development

TypeScript has evolved into a powerful tool for building robust applications. This article explores advanced patterns like conditional types, mapped types, and template literal types that can help you write more expressive and type-safe code.

Fig. 01 — TypeScript's type system enables powerful compile-time guarantees

Conditional Types

Conditional types allow you to create types that depend on other types. They're incredibly powerful for building flexible type systems.

type NonNullable<T> = T extends null | undefined ? never : T;

type Example1 = NonNullable<string | null>; // string
type Example2 = NonNullable<number | undefined>; // number

Distributive Conditional Types

When a conditional type acts on a union type, it becomes distributive:

type ToArray<T> = T extends any ? T[] : never;

type StrArrOrNumArr = ToArray<string | number>; 
// string[] | number[]

Mapped Types

Mapped types allow you to create new types by transforming properties of existing types:

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

type Partial<T> = {
  [P in keyof T]?: T[P];
};

Template Literal Types

Template literal types enable you to create types from string templates:

type EventName<T extends string> = `on${Capitalize<T>}`;

type ClickEvent = EventName<'click'>; // 'onClick'
type SubmitEvent = EventName<'submit'>; // 'onSubmit'

Real-World Applications

These patterns come together to create powerful type utilities that make your codebase more maintainable and less error-prone.

"TypeScript's type system is Turing-complete. With advanced patterns, you can express almost any constraint you can imagine."

Conclusion

Mastering these advanced TypeScript patterns will help you build more robust type systems and catch errors at compile time rather than runtime.