想要定义某种由多种类型合并而成的类型使用交叉类型，

    1. type Feature = {
    2.   id: number;
    3.   name: string;
    4. };
    5. type Select = {
    6.   selected: boolean;
    7. };
    8. type FeatureSelect = Feature & Select;
    11. const features: FeatureSelect[] = [
    12.   { id: 1, name: "foo", selected: false },
    13.   { id: 2, name: "bar", selected: false },
    14. ];