title: How to check in an object has key in angular2
body: <p>I have the following object let usersVal = snapshot.val();</p>
  
  <p>The console.log </p>
  
  <pre><code>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
  </code></pre>
  
  <p>I want to check if object has uid key. If it does I set some boolan value to true</p>
  
  <pre><code>this.users = af.database.object('/some-users', { preserveSnapshot: true });
      this.users.subscribe(snapshot =&gt; {
        let usersVal = snapshot.val();
        if(key in usersVal){
          this.userId = true;
        }
  
  });
  </code></pre>
  
  <p>How can I achieve this in an angular2 component?</p>