JavaScript

I am trying to create a page that shows google map and allows users to draw lines on the map and save them.. but when I try to run the page, the map doesn’t show up at all. What am I doing wrong? the page is literally blank with the form at the end.

I was having a look online for a solution.. I found this code and modified it with my api key

<!DOCTYPE html>
<html>
  <head>
    <title>Draw </title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <style>
    html,
    body,
    #map-canvas {
      height: 90%;
      margin: 0px;
      padding: 0px
    }
    </style>
<script type="text/javascript">
            var map; // Global declaration of the map
            var iw = new google.maps.InfoWindow(); // Global declaration of the infowindow
            var lat_longs = new Array();
            var markers = new Array();
            var drawingManager;
            function initialize() {
                 var myLatlng = new google.maps.LatLng(40.9403762, -74.1318096);
                var myOptions = {
                    zoom: 13,
                    center: myLatlng,
                    mapTypeId: google.maps.MapTypeId.ROADMAP}
                map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
                drawingManager = new google.maps.drawing.DrawingManager({
                drawingMode: google.maps.drawing.OverlayType.POLYGON,
                drawingControl: true,
                drawingControlOptions: {
                    position: google.maps.ControlPosition.TOP_CENTER,
                    drawingModes: [google.maps.drawing.OverlayType.POLYGON]
                },
                        polygonOptions: {
                            editable: true
                        }
            });
            drawingManager.setMap(map);
            
            google.maps.event.addListener(drawingManager, "overlaycomplete", function(event) {
                var newShape = event.overlay;
                newShape.type = event.type;
            });

            google.maps.event.addListener(drawingManager, "overlaycomplete", function(event){
                overlayClickListener(event.overlay);
                $('#vertices').val(event.overlay.getPath().getArray());
            });
        }
function overlayClickListener(overlay) {
    google.maps.event.addListener(overlay, "mouseup", function(event){
        $('#vertices').val(overlay.getPath().getArray());
    });
}
 initialize();

$(function(){
    $('#save').click(function(){
        //iterate polygon vertices?
    });
});
</script>

<script src="https://maps.googleapis.com/maps/api/js?key=[my api key]&libraries=drawing"></script>
<div id="map_canvas" style="width:500px; height:450px;"></div>
<form method="post" accept-charset="utf-8" id="map_form">
    <input type="text" name="vertices" value="" id="vertices"  />
    <input type="button" name="save" value="Save!" id="save"  />
</form>
</body>
</html>

Answer

your HTML is invalid (no end tag for head, no start tag for body).
when you are loading the API synchronously, you need to include it before you use it.
when you are loading the API synchronously, you need to move the javascript after the DOM

working fiddle

code snippet:

<!DOCTYPE html>
<html>
  <head>
    <title>Draw </title>
    <script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
    <script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
    <style>
    html,
    body,
    #map-canvas {
      height: 90%;
      margin: 0px;
      padding: 0px
    }
    </style>
<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&libraries=drawing"></script>
</head>
<body>
<div id="map_canvas" style="width:500px; height:450px;"></div>
<form method="post" accept-charset="utf-8" id="map_form">
    <input type="text" name="vertices" value="" id="vertices"  />
    <input type="button" name="save" value="Save!" id="save"  />
</form>
<script type="text/javascript">
            var map; // Global declaration of the map
            var iw = new google.maps.InfoWindow(); // Global declaration of the infowindow
            var lat_longs = new Array();
            var markers = new Array();
            var drawingManager;
            function initialize() {
                 var myLatlng = new google.maps.LatLng(40.9403762, -74.1318096);
                var myOptions = {
                    zoom: 13,
                    center: myLatlng,
                    mapTypeId: google.maps.MapTypeId.ROADMAP}
                map = new google.maps.Map(document.getElementById("map_canvas"), myOptions);
                drawingManager = new google.maps.drawing.DrawingManager({
                drawingMode: google.maps.drawing.OverlayType.POLYGON,
                drawingControl: true,
                drawingControlOptions: {
                    position: google.maps.ControlPosition.TOP_CENTER,
                    drawingModes: [google.maps.drawing.OverlayType.POLYGON]
                },
                        polygonOptions: {
                            editable: true
                        }
            });
            drawingManager.setMap(map);
            
            google.maps.event.addListener(drawingManager, "overlaycomplete", function(event) {
                var newShape = event.overlay;
                newShape.type = event.type;
            });
            google.maps.event.addListener(drawingManager, "overlaycomplete", function(event){
                overlayClickListener(event.overlay);
                $('#vertices').val(event.overlay.getPath().getArray());
            });
        }
function overlayClickListener(overlay) {
    google.maps.event.addListener(overlay, "mouseup", function(event){
        $('#vertices').val(overlay.getPath().getArray());
    });
}
 initialize();
$(function(){
    $('#save').click(function(){
        //iterate polygon vertices?
    });
});
</script>
</body>
</html>

Javascript – Google map not displaying

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Answer