Mastering TypeScript in 2025

TypeScript has become the de facto standard for building large-scale JavaScript applications. Let's explore its most powerful features.

Type System Fundamentals

Union and Intersection Types

type User = {
  id: string;
  name: string;
};

type Admin = User & {
  permissions: string[];
};

type Status = 'active' | 'inactive' | 'pending';

Generics

Make your code reusable with generics:

function identity<T>(arg: T): T {
  return arg;
}

const result = identity<string>("Hello");

Advanced Patterns

Conditional Types

type IsString<T> = T extends string ? true : false;

type A = IsString<string>; // true
type B = IsString<number>; // false

Template Literal Types

type Color = 'red' | 'blue' | 'green';
type Shade = 'light' | 'dark';

type ColorShade = `${Shade}-${Color}`;
// 'light-red' | 'light-blue' | 'light-green' | 'dark-red' | ...

Best Practices

1. Use strict mode: Always enable strict in tsconfig.json
2. Avoid any: Use unknown when you don't know the type
3. Leverage inference: Let TypeScript infer types when possible
4. Type your APIs: Always type function parameters and returns
5. Use utility types: Leverage built-in utilities like Partial, Pick, Omit

Utility Types

TypeScript provides powerful utility types:

interface User {
  id: string;
  name: string;
  email: string;
  age: number;
}

type PartialUser = Partial<User>;
type UserPreview = Pick<User, 'id' | 'name'>;
type UserWithoutEmail = Omit<User, 'email'>;

Conclusion

TypeScript's type system is incredibly powerful. Master it to write better, safer code!