Fade In circles in Google Maps

Question

On my map, I have it so that a node/circle is drawn at a certain location, and when this node is clicked, other related nodes appear nearby. However, I'd like to have them fade in after about one second instead of just appearing suddenly. I already had a look at this solution, but I couldn't really understand how it would translate over to my code. Is there an easy way to do this?

...

function initialize()
            {
            for(var num = 0; num < lat.length; num++)
            {
                nodeInfo[num] = 
                {
                    center: new google.maps.LatLng(lat[num], lon[num])
                }
            }

                // Styles
                var styles = [
                    {
                        stylers: [
                            {
                                hue: "#2222EE"
                            },
                            {
                                saturation: -40
                            }
                        ]
                    },
                    {
                        featureType: "road",
                        elementType: "geometry",
                        stylers: [
                            {
                                lightness: 100
                            },
                            {
                                visibility: "simplified"
                            }
                        ]
                    },
                    {
                        featureType: "road",
                        elementType: "labels",
                        stylers: [
                            {
                                visibility: "off"
                            }
                        ]
                    },
                    {
                        featureType: "transit.station.bus",
                        elementType: "labels.icon",
                        stylers: [
                            {
                                visibility: "off"
                            }
                        ]
                    }               
                ];

                var styledMap = new google.maps.StyledMapType(styles,
                {name: "Styled Map"});

                // Options for map
                var mapOptions =
                {
                    center: new google.maps.LatLng(42.35791, -71.063157),
                    zoom: 17,
                    mapTypeControlOptions:
                    {
                        mapTypeIds: [google.maps.MapTypeId.ROADMAP, 'map_style']
                    }               
                };

                map = new google.maps.Map(document.getElementById("map-canvas"), mapOptions);

                map.mapTypes.set('map_style', styledMap);
                map.setMapTypeId('map_style');

                nodeDisplay();  
            }       

            function nodeDisplay()
            {
                var drawNode;

                for(var i in nodeInfo)
                {   
                    if(i >= 1)
                    {
                        if(nodeSelect == true)
                        {
                            drawNode = {
                                strokeColor: '#0000FF',
                                fillColor: '#0000FF',
                                strokeWeight: 2,
                                fillOpacity: 1,
                                map: map,
                                center: nodeInfo[i].center,
                                radius: 4,
                                visible: true
                            };
                        }
                        else
                        {
                            drawNode = {
                                strokeColor: '#0000FF',
                                fillColor: '#0000FF',
                                strokeWeight: 2,
                                fillOpacity: 1,
                                map: map,
                                center: nodeInfo[i].center,
                                radius: 4,
                                visible: false
                            };
                        }
                    }
                    else
                    {
                        drawNode = {
                            strokeColor: '#FF0000',
                            fillColor: '#FF0000',
                            strokeWeight: 2,
                            fillOpacity: 1,
                            map: map,
                            center: nodeInfo[i].center,
                            radius: 6
                        };
                    }

                    node[i] = new google.maps.Circle(drawNode);
                    attachMessage(i);
                }
            }

            function clearOverlays()
            {
                for(var i in nodeInfo)
                {
                    if(i > 0)
                    {
                        node[i].setMap(null);
                    }
                }
            }

            function attachMessage(number)
            {
                var message = "Hello. This is node number " + number + ".";
                var infowindow = new google.maps.InfoWindow({
                    size: new google.maps.Size(50, 50)
                });

                infowindow.content = message;

                google.maps.event.addListener(node[number], 'click', function()
                {
                    //infowindow.open(map, node[number]);
                    clearOverlays();
                    nodeSelect = !nodeSelect;
                    nodeDisplay();
                });     
            }

            google.maps.event.addDomListener(window, 'load', initialize);

Answer 1

Fade the circles in (start at zero, end at one):

function polygon_fadein(polygon, seconds, callback){
    polygon.setOptions({fillOpacity:0, strokeOpacity:0});
    //  The "fade task" runs every 50 ms, seconds is the total time to fade,
    //   multiplied by approximately 1000 to turn it into milliseconds.
    var fill = 50/(seconds*999);
    var stroke = 50/(seconds*999);
    var fadein = setInterval(function(){
        if((polygon.get("strokeOpacity") > 0.99) &&  (polygon.get("fillOpacity") > 0.99)){
            clearInterval(fadein);
            if(typeof(callback) == 'function')
                callback();
            return;
        }
        polygon.setOptions({
            'fillOpacity': Math.min(1.0, polygon.fillOpacity+fill),
            'strokeOpacity': Math.min(1.0, polygon.strokeOpacity+stroke)
        });
    }, 50);
}

code snippet:

var nodeSelect = true;
// Boston 42.3584308, -71.0597732
var lat = [42.350542, 42.353036, 42.358249, 42.350101, 42.350190, 42.3634819];
var lon = [-71.074856, -71.059052, -71.057507, -71.087478, -71.059300, -71.0686226];
var nodeInfo = [];
var node = [];
var map = null;

function initialize() {
  for (var num = 0; num < lat.length; num++) {
    nodeInfo[num] = {
      center: new google.maps.LatLng(lat[num], lon[num])
    }
  }

  var styledMap = new google.maps.StyledMapType(styles, {
    name: "Styled Map"
  });

  // Options for map
  var mapOptions = {
    center: new google.maps.LatLng(42.35791, -71.063157),
    zoom: 15,
    mapTypeControlOptions: {
      mapTypeIds: [google.maps.MapTypeId.ROADMAP, 'map_style']
    }
  };

  map = new google.maps.Map(document.getElementById("map-canvas"), mapOptions);

  map.mapTypes.set('map_style', styledMap);
  map.setMapTypeId('map_style');

  nodeDisplay();
}

function nodeDisplay() {
  var drawNode;

  for (var i in nodeInfo) {
    if (i >= 1) {
      if (nodeSelect == true) {
        drawNode = {
          strokeColor: '#0000FF',
          fillColor: '#FF0000', //'#0000FF',
          strokeWeight: 2,
          fillOpacity: 1,
          map: map,
          center: nodeInfo[i].center,
          radius: 40,
          visible: true
        };

      } else {
        drawNode = {
          strokeColor: '#0000FF',
          fillColor: '#FF0000', //'#0000FF',
          strokeWeight: 2,
          fillOpacity: 1,
          map: map,
          center: nodeInfo[i].center,
          radius: 40,
          visible: false
        };
      }
    } else {
      drawNode = {
        strokeColor: '#FF0000',
        fillColor: '#FF0000',
        strokeWeight: 2,
        fillOpacity: 1,
        map: map,
        center: nodeInfo[i].center,
        radius: 60
      };
    }

    node[i] = new google.maps.Circle(drawNode);
    polygon_fadein(node[i], 5);
    attachMessage(i);
  }
}

function clearOverlays() {
  for (var i in nodeInfo) {
    if (i > 0) {
      node[i].setMap(null);
    }
  }
}

function attachMessage(number) {
  var message = "Hello. This is node number " + number + ".";
  var infowindow = new google.maps.InfoWindow({
    size: new google.maps.Size(50, 50)
  });

  infowindow.setContent(message);

  google.maps.event.addListener(node[number], 'click', function() {
    infowindow.setPosition(node[number].getCenter());
    infowindow.open(map);
  });
}

function polygon_fadein(polygon, seconds, callback) {
  polygon.setOptions({
    fillOpacity: 0,
    strokeOpacity: 0
  });
  var fill = 50 / (seconds * 999);
  var stroke = 50 / (seconds * 999);
  var fadein = setInterval(function() {
    if ((polygon.get("strokeOpacity") > 0.99) && (polygon.get("fillOpacity") > 0.99)) {
      clearInterval(fadein);
      if (typeof(callback) == 'function')
        callback();
      return;
    }
    polygon.setOptions({
      'fillOpacity': Math.min(1.0, polygon.fillOpacity + fill),
      'strokeOpacity': Math.min(1.0, polygon.strokeOpacity + stroke)
    });
  }, 50);
}

google.maps.event.addDomListener(window, 'load', initialize);

// Styles
var styles = [{
  stylers: [{
    hue: "#2222EE"
  }, {
    saturation: -40
  }]
}, {
  featureType: "road",
  elementType: "geometry",
  stylers: [{
    lightness: 100
  }, {
    visibility: "simplified"
  }]
}, {
  featureType: "road",
  elementType: "labels",
  stylers: [{
    visibility: "off"
  }]
}, {
  featureType: "transit.station.bus",
  elementType: "labels.icon",
  stylers: [{
    visibility: "off"
  }]
}];

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

<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk"></script>
<div id="map-canvas" style="height: 600px; width:800px;"></div>
<div id="polygonCoords"></div>

(original code in the question most likely from: Is there a way to fade out a V3 google.maps.Polygon?)