HTML and CSS Reference
In-Depth Information
number to the
clearWatch()
method to stop watching the user's location. The code in Listing 12-12 shows
how you can use
watchPosition()
and
clearWatch()
.
Listing 12-12.
Using the
watchPosition()
and
clearWatch()
Methods
var watchId;
function StartWatch() {
watchId = window.navigator.geolocation.watchPosition(OnSuccess, OnError);
}
function StopWatch() {
window.navigator.geolocation.clearWatch(watchId);
};
This code defines a global variable named
watchId
to store the watch handle returned by
watchPosition()
. The
StartWatch()
function calls
geolocation
object's
watchPosition()
method and
passes
OnSuccess
and
OnError
callback functions as before. The returned numeric handle is stored in the
watchId
variable.
StopWatch()
calls the
geolocation
object's
clearWatch()
method and passes
watchId
as a
parameter to clear that watch.
Summary
The Geolocation API allows you to find the user's geographic location in terms of latitude and longitude.
The
geolocation
object property of the
navigator
object exposes the methods responsible for retrieving
the user's location. The
getCurrentPosition()
method returns the user's current location. The
watchPosition()
method keeps monitoring that location until the
clearWatch()
method is called.
Using the Geolocation API, you can build location-aware web applications that present data based on
the user's location. You can also integrate the Geolocation API with mapping services such as Google Maps
and Bing Maps.
You've learned about all of HTML5's prominent programmable features. Although, as a web developer,
your core focus is on programmable features, at times you also need to style your web applications using
Cascading Style Sheets (CSS). CSS3 offers the latest in this area. The next chapter covers some new and
improved features.
