Peter Lubbers - Pro HTML 5 Programming

CHAPTER 4 ■ USING THE HTML5 GEOLOCATION API
• POSITION_UNAVAILABLE (error code 2)—The technique used to determine the user’s
location was attempted, but failed.
• TIMEOUT (error code 3)—A timeout value was set as an option, and the attempt to
determine the location exceeded that limit.
In these cases, you will probably want to let the user know that something went wrong. You may
want to retry getting the values in the case of an unavailable or timed-out request.
Listing 4-4 shows an example of an error handler in action.
Listing 4-4. Using an error handler
function handleLocationError(error) {
switch(error.code){
case 0:
updateStatus("There was an error while retrieving your location: " +
error.message);
break;
case 1:
updateStatus("The user prevented this page from retrieving a location.");
break;
case 2:
updateStatus("The browser was unable to determine your location: " +
error.message);
break;
case 3:
updateStatus("The browser timed out before retrieving the location.");
break;
}
}
The error codes are accessed from the code attribute of the provided error object, while the message
attribute will give access to a more detailed description of what went wrong. In all cases, we call our own
routine to update the status of the page with the necessary info.
Optional Geolocation Request Attributes
With both the normal and error cases handled, you should turn your attention to the three optional
attributes that you can pass to the HTML5 Geolocation service in order to fine-tune how it gathers its
data. Note that these three attributes can be passed using shorthand object notation, making it trivial to
add them to your HTML5 Geolocation request calls.
• enableHighAccuracy—This is a hint to the browser that, if available, you would like
the HTML5 Geolocation service to use a higher accuracy-detection mode. This
defaults to false, but when turned on, it may not cause any difference, or it may
cause the machine to take more time or power to determine location. Use with
caution.
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