multiple markers on google maps from firebase database

Answer 1

You now have multiple positions in your data.

The code works if you change it to read the data format in your database. You have your coordinates in an array named l in the User object.

locationsRef.on('child_added', function(snapshot) {
  var data = snapshot.val();
  var marker = new google.maps.Marker({
    position: {
      lat: data.User.l[0],
      lng: data.User.l[1]
    },
    map: map
  });
  bounds.extend(marker.getPosition());
  marker.addListener('click', (function(data) {
    return function(e) {
      infowindow.setContent(this.getPosition().toUrlValue(6) + "<br>" + data.User.g);
      infowindow.open(map, this);
    }
  }(data)));
  map.fitBounds(bounds);
});

proof of concept fiddle

code snippet:

function initialize() {
  var infowindow = new google.maps.InfoWindow();
  var map = new google.maps.Map(
    document.getElementById("map_canvas"), {
      center: new google.maps.LatLng(37.4419, -122.1419),
      zoom: 13,
      mapTypeId: google.maps.MapTypeId.ROADMAP
    });
  // Initialize Firebase
  var config = {
    apiKey: "AIzaSyCWZjRe2CK8Hu2VN35AgZOQ7lQZKcI-UWM",
    authDomain: "carrier-35d7c.firebaseapp.com",
    databaseURL: "https://carrier-35d7c.firebaseio.com",
    projectId: "carrier-35d7c",
    storageBucket: "carrier-35d7c.appspot.com",
    messagingSenderId: "827792028763"
  };
  firebase.initializeApp(config);

  //Create a node at firebase location to add locations as child keys
  var locationsRef = firebase.database().ref("locations");
  var bounds = new google.maps.LatLngBounds();
  locationsRef.on('child_added', function(snapshot) {
    console.log(snapshot)
    var data = snapshot.val();
    console.log(data);
    var marker = new google.maps.Marker({
      position: {
        lat: data.User.l[0],
        lng: data.User.l[1]
      },
      map: map
    });
    bounds.extend(marker.getPosition());
    marker.addListener('click', (function(data) {
      return function(e) {
        infowindow.setContent(this.getPosition().toUrlValue(6) + "<br>" + data.User.g);
        infowindow.open(map, this);
      }
    }(data)));
    map.fitBounds(bounds);
  });
}
google.maps.event.addDomListener(window, "load", initialize);

html,
body,
#map_canvas {
  height: 100%;
  width: 100%;
  margin: 0px;
  padding: 0px
}

<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>
<script src="https://www.gstatic.com/firebasejs/4.12.1/firebase.js"></script>
<script src="https://cdn.firebase.com/libs/geofire/4.1.2/geofire.min.js"></script>
<div id="map_canvas"></div>