typescript 高级用法

[CPPAlien]

• Pick<User, "id" | "age">

• Partial

• Required

• T extends U ? X : Y

• Exclude

  // 相当于: type A = 'a'
  type A = Exclude<'x' | 'a', 'x' | 'y' | 'z'>

• Omit

  // 相当于: type PickUser = { age: number; name: string; }
  type OmitUser = Omit<User, "id">

-is TypeScript will narrow that variable to that specific type if the original type is compatible

function isFish(pet: Fish | Bird): pet is Fish {
    return (pet as Fish).swim !== undefined;
}

if (isFish(pet)) {
    pet.swim();
}

• as 强转

• Record

  type Record<K extends keyof any, T> = {
  };

-Dictionary

interface Dictionary<T> {
  [index: string]: T;
};