索引类型

function pluck<T,K extends keyof T>(o: T , names:K[]) : T[K][]{
    return names.map(n => o[n]);
}

interface Person{
    name:string;
    age:number;
}

let person : Person = {
    name:'Jarid',
    age:36
}

let strings: string[] = pluck(person,['name']);
console.log(strings);

映射类型