マップの初期化が完了するまで使用できません。アクセスする前に、「projection_changed」イベントを待つ必要があります。
function initialize() {
var mapOptions = {
zoom: 8,
center: new google.maps.LatLng(-34.397, 150.644),
mapTypeId: google.maps.MapTypeId.ROADMAP
};
map = new google.maps.Map(document.getElementById('map-canvas'),
mapOptions);
google.maps.event.addListenerOnce(map,"projection_changed", function() {
alert("projection:"+map.getProjection());
});
}
概念実証フィドル
コードスニペット:
function initialize() {
var mapOptions = {
zoom: 8,
center: new google.maps.LatLng(-34.397, 150.644),
mapTypeId: google.maps.MapTypeId.ROADMAP
};
map = new google.maps.Map(document.getElementById('map-canvas'),
mapOptions);
google.maps.event.addListenerOnce(map, "projection_changed", function() {
console.log("projection:" + map.getProjection());
document.getElementById('output').innerHTML = "map.getProjection()=" + JSON.stringify(map.getProjection(), null, ' ');
});
}
/* Always set the map height explicitly to define the size of the div
* element that contains the map. */
#map-canvas {
height: 80%;
}
/* Optional: Makes the sample page fill the window. */
html,
body {
height: 100%;
margin: 0;
padding: 0;
}
<!DOCTYPE html>
<html>
<head>
<title>Simple Map</title>
<script src="https://polyfill.io/v3/polyfill.min.js?features=default"></script>
<!-- jsFiddle will insert css and js -->
</head>
<body>
<div id="output"></div>
<div id="map-canvas"></div>
<!-- Async script executes immediately and must be after any DOM elements used in callback. -->
<script src="https://maps.googleapis.com/maps/api/js?key=AIzaSyCkUOdZ5y7hMm0yrcCQoCvLwzdM6M8s5qk&callback=initialize&libraries=&v=weekly" async></script>
</body>
</html>