Mastering TypeScript

TypeScript has become the standard for building large-scale JavaScript applications. But beyond the basics of types and interfaces, there's a world of advanced patterns that can make your code more robust and maintainable.

Advanced Type Patterns

Discriminated Unions

type Shape =
  | { kind: 'circle'; radius: number }
  | { kind: 'rectangle'; width: number; height: number }
  | { kind: 'triangle'; base: number; height: number };

function area(shape: Shape): number {
  switch (shape.kind) {
    case 'circle': return Math.PI * shape.radius ** 2;
    case 'rectangle': return shape.width * shape.height;
    case 'triangle': return (shape.base * shape.height) / 2;
  }
}

Template Literal Types

type EventName = 'click' | 'focus' | 'blur';
type Handler = `on${Capitalize<EventName>}`;
// Result: "onClick" | "onFocus" | "onBlur"

Generic Patterns

Mastering generics allows you to write reusable, type-safe code:

• Generic Constraints: Use extends to limit generic types
• Conditional Types: Create types that depend on other types
• Mapped Types: Transform existing types into new ones

Best Practices

1. Prefer interfaces for object shapes and types for unions
2. Use strict mode for maximum type safety
3. Leverage the type system to make illegal states unrepresentable
4. Write self-documenting code with descriptive type names

TypeScript is more than just a tool — it's a mindset that leads to better, more reliable code.