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.

c23f001.tif

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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