Explanation of the use of async defer for the Google Maps API
Question
I'm trying to understand the loading of the <script> elements in the code snippet at https://developers.google.com/maps/documentation/javascript/tutorial :
<!DOCTYPE html>
<html>
<head>
<title>Simple Map</title>
<meta name="viewport" content="initial-scale=1.0">
<meta charset="utf-8">
<style>
/* Always set the map height explicitly to define the size of the div
* element that contains the map. */
#map {
height: 100%;
}
/* Optional: Makes the sample page fill the window. */
html, body {
height: 100%;
margin: 0;
padding: 0;
}
</style>
</head>
<body>
<div id="map"></div>
<script>
var map;
function initMap() {
map = new google.maps.Map(document.getElementById('map'), {
center: {lat: -34.397, lng: 150.644},
zoom: 8
});
}
</script>
<script src="https://maps.googleapis.com/maps/api/js?key=YOUR_API_KEY&callback=initMap"
async defer></script>
</body>
</html>
Presumably, the google.maps.Map object is defined in the latter script . However, that script has the async defer attributes, which according to https://developer.mozilla.org/en-US/docs/Web/HTML/Element/script means that it will be executed asynchronously and after the document has been parsed. But since this comes after the first script , how can the first script instantiate a Map before the definition has been loaded?
1 answers
solution1
0 ACCPTED 2018-08-19 22:14:36
要将 Charlie 的评论转换为答案，Google Maps API src末尾的&callback=initMap确保在 Google Maps 加载完成后调用initMap函数。
The technical post webpages of this site follow the CC BY-SA 4.0 protocol. If you need to reprint, please indicate the site URL or the original address.Any question please contact:yoyou2525@163.com.