映射
將一個集合中的每個元素與另一個元素關聯的動作。
TypeScript中的映射類型
允許你通過轉換現有類型的屬性來創建新的類型。
範例
type MoviesByGenre = {
action: ‘Die Hard’;
comedy: ‘Groundhog Day’;
sciFi: ‘Blade Runner’;
fantasy: ‘The Lord of the Rings: The Fellowship of the Ring’;
drama: ‘The Shawshank Redemption’;
horror: ‘The Shining’;
romance: ‘Titanic’;
animation: ‘Toy Story’;
thriller: ‘The Silence of the Lambs’;
};
action: ‘Die Hard’;
comedy: ‘Groundhog Day’;
sciFi: ‘Blade Runner’;
fantasy: ‘The Lord of the Rings: The Fellowship of the Ring’;
drama: ‘The Shawshank Redemption’;
horror: ‘The Shining’;
romance: ‘Titanic’;
animation: ‘Toy Story’;
thriller: ‘The Silence of the Lambs’;
};
//透過映射來定義新型別MovieInfoByGenre
type MovieInfoByGenre<T> = {
//**in**專為映射所使用的運算子，告訴TypeScript，K為**in**運算子右邊集合內的單一元素
//**keyof T**: T物件所有鍵(Property)的聯集
[K in keyof T]: {
name: string;
year: number;
director: string;
};
};
type MovieInfoByGenre<T> = {
//**in**專為映射所使用的運算子，告訴TypeScript，K為**in**運算子右邊集合內的單一元素
//**keyof T**: T物件所有鍵(Property)的聯集
[K in keyof T]: {
name: string;
year: number;
director: string;
};
};
type Example = MovieInfoByGenre<MoviesByGenre>;
/*Example為: {
action: {
name: string;
year: number;
director: string;
};
comedy: {
name: string;
year: number;
director: string;
};
sciFi: {
name: string;
year: number;
director: string;
};
fantasy: {
name: string;
year: number;
director: string;
};
drama: {
name: string;
year: number;
director: string;
};
horror: {
name: string;
year: number;
director: string;
};
romance: {
name: string;
year: number;
director: string;
};
animation: {
name: string;
year: number;
director: string;
};
thriller: {
name: string;
year: number;
director: string;
};
}*/
