Mastering TypeScript: Advanced Patterns and Techniques

TypeScript has evolved into one of the most powerful tools in modern web development. Let's explore advanced patterns that will make you a TypeScript expert.

Utility Types Deep Dive

TypeScript provides powerful utility types that can transform your type definitions:

// Partial - makes all properties optional
interface User {
  id: string;
  name: string;
  email: string;
}
type PartialUser = Partial;
// { id?: string; name?: string; email?: string; }
// Pick - select specific properties
type UserName = Pick;
// { name: string; }
// Omit - exclude specific properties
type UserWithoutId = Omit;
// { name: string; email: string; }

Conditional Types

Create types that depend on other types:

type NonNullable = T extends null | undefined ? never : T;
type ApiResponse = T extends string
  ? { message: T }
  : T extends number
  ? { count: T }
  : { data: T };
// Usage
type StringResponse = ApiResponse; // { message: string }
type NumberResponse = ApiResponse; // { count: number }
type ObjectResponse = ApiResponse;   // { data: User }

Template Literal Types

Create string literal types with patterns:

type EventName = on${Capitalize};
type ClickEvent = EventName<'click'>; // 'onClick'
type SubmitEvent = EventName<'submit'>; // 'onSubmit'
// Advanced example
type CSSProperty = --${T};
type CustomProperty = CSSProperty<'primary-color'>; // '--primary-color'

Mapped Types

Transform existing types:

type Readonly = {
  readonly [P in keyof T]: T[P];
};
type Optional = Omit & Partial>;
// Usage
interface User {
  id: string;
  name: string;
  email: string;
}
type UserWithOptionalEmail = Optional;
// { id: string; name: string; email?: string; }

Advanced Generic Constraints

// Constrain generic to have specific properties
function processEntity(
  entity: T
): T & { processed: boolean } {
  return {
    ...entity,
    processed: true
  };
}
// Multiple constraints
function merge(
  target: T,
  source: U
): T & U {
  return { ...target, ...source };
}

Conclusion

These advanced TypeScript patterns will help you write more robust, type-safe code. Practice implementing them in your projects to become a TypeScript expert.