September 2012
Intermediate to advanced
552 pages
14h 48m
English
Content preview from Professional HTML5 Mobile Game Development
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Getting a One-Time Position
Getting the position of the user is simple enough; just call navigator.geolocation.getCurrentPosition with a callback. This triggers a notification at the top of the browser, as shown in Figure 23-1, giving the user the power to allow or deny the request. If you supply a second callback, that callback is called if the browser couldn’t get the location due to a denied request or other error.
Figure 23-1: The geolocation permission dialog.
To see the data in the console that’s returned from a request, you can enter the code in Listing 23-1 into a file called position.html, load the page in a desktop browser, and open up the JavaScript console.
Listing 23-1: Getting a one-time position
<!DOCTYPE HTML>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Grabbing the position</title>
</head>
<body>
<script>
function logPosition(position) {
console.log(position);
}
function positionError(error) {
console.log(error);
}
navigator.geolocation.getCurrentPosition(logPosition,positionError);
</script>
</body>
</html>Examining the console shows you the result of the request. If you denied the request or the system couldn’t look up your location, the positionError method is called with a PositionError object. If you run this from a file:// URL, Chrome will give you an error by default so you’ll want to run it from localhost.
If the geolocation was successful, ...
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