javascript - 如何 checkin 对象在angular2中有键

Question

我有以下对象 let usersVal = snapshot.val();

控制台日志

3TngNGbwMVhc5kJ2b3wAULEIP6g1
    Object
    photoUrl
    "https://scontent.xx.fbcdn.net/v/t1.0-1/ss"
    provider
    "facebook.com"
    signup
    1480596548396
    useremail
    "someemail@yahoo.com"
    username
    "James nan"
    __proto__


 c834vePyJ3SFVk2iO4rU0ke1cSa2
    photoUrl
    "https://firebasestorage.googleapis.com/v0/b/ff"
    provider
    "google.com"
    signup
    1480600290735
    useremail
    "3333@gmail.com"
    username
    "Ericel123eessdd"
    __proto__
    Object

我想检查对象是否有 uid 键。如果是这样，我将一些 bool 值设置为 true

this.users = af.database.object('/some-users', { preserveSnapshot: true });
    this.users.subscribe(snapshot => {
      let usersVal = snapshot.val();
      if(key in usersVal){
        this.userId = true;
      }

});

如何在 angular2 组件中实现这一点？

Answer 1

应该像

一样简单

let usersVal = snapshot.val();
if (usersVal["uid"]) {
    ...
}