Why isn't this an instance of map of google.maps.Map? InvalidValueError: setMap: not an instance of Map;

Question

I am getting the error Assertion failed: InvalidValueError: setMap: not an instance of Map; and not an instance of StreetViewPanorama on a google map web page. I th

Answer 1

The map variable that is an instance of a google.maps.Map is local to the initialize function. The map variable in the createMarker function is undefined. One option: define the variable in the global scope:

var map;

then just initialize it in the initialize function:

function initialize(){
    var mapProp = {
        center: new google.maps.LatLng(38, -78),
        zoom: 10,
        mapTypeId: google.maps.MapTypeId.ROADMAP
    };
    map = new google.maps.Map(document.getElementById('map'), mapProp);
};

proof of concept fiddle

code snippet:

var map;

function initialize() {
  var mapProp = {
    center: new google.maps.LatLng(38, -78),
    zoom: 6,
    mapTypeId: google.maps.MapTypeId.ROADMAP
  };
  map = new google.maps.Map(document.getElementById('map'), mapProp);
};

$(document).ready(function() {
  var url = 'https://opendata.howardcountymd.gov/resource/96q9-qbh7.json';
  initialize();
  $.getJSON(url, function(data) {
    $.each(data, function(i, field) {
      $('#list').append("
" + data[i].location.longitude + " & " + data[i].location.latitude + "
");
      createMarker(data);

      function createMarker(data) {
        var marker = new google.maps.Marker({
          position: new google.maps.LatLng(data[i].location.latitude, data[i].location.longitude),
          map: map,
          title: field.crossroad
        });
      };
    });
  });

});

#map {
  height: 300px;
  width: 600px;
  border: 1px solid black;
  margin: 0 auto;
}

Hello World

Another option would be to return the map from the initialize function