相关疑难解决方法(0)

给出以下代码

interface IPerson {
   firstName: string;
   lastName: string;
}

var persons: { [id: string]: IPerson; } = {
   "p1": { firstName: "F1", lastName: "L1" },
   "p2": { firstName: "F2" }
};

为什么不初始化被拒绝？毕竟,第二个对象没有"lastName"属性.