Delete Polygon when creating a new one

Question

I have a small google map https://jsfiddle.net/deMischa/fkLm5zg9/8/. If you click on it, a marker will be placed and a circle will be drawn around that marker.

If you click again, the marker is deleted and a new one is placed. That works fine.

function addMarker(location,blue) {  
  deleteMarkers();

  var marker = new google.maps.Marker({  
    position: location,  
    map: map,
    draggable: true
  });  
  markers.push(marker);  
  window.position = markers[0].position;

  addCircle();
}  

My problem is that I can't do the same thing with the polygon/circle.

I know that I can delete a polygon with

function deleteCircle() { 
  blue.setMap(null);
} 

And if I call that function from a button click, it's working. But I want this to be called from the function, that creates a new marker/circle. And here it is not working

function addMarker(location,blue) {  
  deleteMarkers();
  deleteCircle(); LIKE THE MARKERS, THE CIRCLES SHOULD BE DELETED HERE

  ...
}  

There is the following error in console

Uncaught TypeError: Cannot read properties of null (reading 'setMap')

Do you guys have any idea? I uploaded the whole script to https://jsfiddle.net/deMischa/fkLm5zg9/8/ so it might be easy to debug.

Answer 1

When I uncomment out the deleteCircle call, I get the following javascript error: Uncaught ReferenceError: blue is not defined, because blue is not defined until you have called the addCircle function for the first time.

Duplicate/related questions:

1. how to remove previous circle from the map?
2. How to remove previous circle automatically before adding new circle in Google map

Suggestion: You declare circle in the global scope but don't use it.

1. change blue to circle.

// Adds a circle to the position of the marker. 
function addCircle() {
  circle = new google.maps.Polygon({
    paths: [drawCircle(new google.maps.LatLng(position), 0.1, 1)],
    strokeColor: "#0000FF",
    strokeOpacity: 0.5,
    strokeWeight: 2,
    fillColor: "white",
    fillOpacity: 0.15
  });
  circle.setMap(map);
}

2. check to see if the circle exists, then hide/delete it if it exists.

// Delete the circle 
function deleteCircle() { 
  if (circle && circle.setMap) 
    circle.setMap(null);
}  

proof of concept fiddle

code snippet:

var map = null;
var circle = null;
var bounds = null;
var markerPosition = null;
var markers = [];
var position = new google.maps.LatLng(50.2275, 7.4885);

function initialize() {
  var myOptions = {
    zoom: 15,
    center: position,
    mapTypeControl: false,
    navigationControl: true,
    mapTypeId: google.maps.MapTypeId.HYBRID
  }

  map = new google.maps.Map(document.getElementById("map"), myOptions);
  bounds = new google.maps.LatLngBounds();

  // This event listener will call addMarker() when the map is clicked.  
  map.addListener('click', function(event) {
    addMarker(event.latLng);
  });
}


// Adds a circle to the position of the marker. 
function addCircle() {
  circle = new google.maps.Polygon({
    paths: [drawCircle(new google.maps.LatLng(position), 0.1, 1)],
    strokeColor: "#0000FF",
    strokeOpacity: 0.5,
    strokeWeight: 2,
    fillColor: "white",
    fillOpacity: 0.15
  });
  circle.setMap(map);
}

// Delete the circle 
function deleteCircle() {
  if (circle && circle.setMap)
    circle.setMap(null);
}


// Adds a marker to the map and push to the array.  
function addMarker(location) {
  deleteMarkers();
  deleteCircle(); //LIKE THE MARKERS, THE CIRCLES SHOULD BE DELETED HERE

  var marker = new google.maps.Marker({
    position: location,
    map: map,
    draggable: true
  });
  markers.push(marker);
  window.position = markers[0].position;

  addCircle();
}

// Sets the map on all markers in the array.  
function setMapOnAll(map) {
  for (var i = 0; i < markers.length; i++) {
    markers[i].setMap(map);
  }
}

// Removes the markers from the map, but keeps them in the array.  
function clearMarkers() {
  setMapOnAll(null);
}

// Deletes all markers in the array by removing references to them.  
function deleteMarkers() {
  clearMarkers();
  markers = [];
}

function drawCircle(point, radius, dir) {
  var d2r = Math.PI / 180; // degrees to radians 
  var r2d = 180 / Math.PI; // radians to degrees 
  var earthsradius = 3963; // 3963 is the radius of the earth in miles

  var points = 64;

  // find the radius in lat/lon 
  var rlat = (radius / earthsradius) * r2d;
  var rlng = rlat / Math.cos(point.lat() * d2r);


  var extp = new Array();
  if (dir == 1) {
    var start = 0;
    var end = points + 1
  } // one extra here makes sure we connect the
  else {
    var start = points + 1;
    var end = 0
  }
  for (var i = start;
    (dir == 1 ? i < end : i > end); i = i + dir) {
    var theta = Math.PI * (i / (points / 2));
    ey = point.lng() + (rlng * Math.cos(theta)); // center a + radius x * cos(theta) 
    ex = point.lat() + (rlat * Math.sin(theta)); // center b + radius y * sin(theta) 
    extp.push(new google.maps.LatLng(ex, ey));
    bounds.extend(extp[extp.length - 1]);
  }
  // alert(extp.length);
  return extp;
}

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

.map {
  height: 80%;
  width: 100%;
}

<!doctype html>
<html lang="en">

<head>
  <meta charset="utf-8">
  <script src="https://maps.googleapis.com/maps/api/js?v=3&key=AIzaSyDCA7_eY2neZvNFOM8jhvjeTpuRS1-HkDU"></script>
  <script src="ol3gm.js"></script>
  <script src="math.js"></script>
  <title>Example</title>
</head>

<body onload="initialize()">
  <div id="map" class="map"></div>
  <br>
  <input onclick="deleteMarkers();" type=button value="Delete Markers">
  <input onclick="deleteCircle();" type=button value="Delete Circle">

</body>

</html>