title: How to retrieve multiple keys in Firebase?
body: <p>Considering this data structure:</p>
  
  <pre><code>{
      "users":{
          "user-1":{
              "groups":{
                  "group-key-1":true,
                  "group-key-3":true
              }
          }
      },
      "groups":{
          "group-key-1":{
              "name":"My group 1"
          },
          "group-key-2":{
              "name":"My group 2"
          },
          "group-key-3":{
              "name":"My group 3"
          },
          "group-key-4":{
              "name":"My group 4"
          },
      }
  }
  </code></pre>
  
  <p>I could get the groups of a particular user with:</p>
  
  <pre><code>firebase.database().ref('users/user-1/groups').on(...)
  </code></pre>
  
  <p>Which would give me this object:</p>
  
  <pre><code>{
      "group-key-1":true,
      "group-key-3":true
  }
  </code></pre>
  
  <p>So now I want to retrieve the info for those groups.</p>
  
  <p>My initial instinct would be to loop those keys and do this:</p>
  
  <pre><code>var data = snapshot.val()
  var keys = Object.keys(data)
  
  for (var i = 0; i &lt; keys.length; i++) {
      firebase.database().ref('groups/' + keys[i]).on(...)
  }
  </code></pre>
  
  <p>Is this the appropriate way to call multiple keys on the same endpoint in Firebase?</p>
  
  <p>Does Firebase provide a better way to solve this problem?</p>