Advanced TypeScript

Advanced TypeScript

Các topic nâng cao cho TypeScript power users.

Mapped Types

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

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

Conditional Types

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

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

Template Literal Types

type EmailLocale = "en" | "vi";
type EmailType = "welcome" | "reset";

type EmailTemplate = `${EmailLocale}_${EmailType}`;
// "en_welcome" | "en_reset" | "vi_welcome" | "vi_reset"

Decorators (Experimental)

function log(target: any, key: string) {
  console.log(`${key} was called`);
}

class MyClass {
  @log
  myMethod() {
    // ...
  }
}

Best Practices

1. Prefer interfaces over types cho object shapes
2. Use strict mode trong tsconfig.json
3. Avoid any - dùng unknown nếu cần
4. Enable strictNullChecks
5. Document complex types

Resources

• TypeScript Handbook
• TypeScript Deep Dive