Java Reference
In-Depth Information
if(window.localStorage) {
superman = JSON.parse(localStorage.getItem("superman"));
}
The Web Storage API provides a useful way of storing various types of information on a
user's computer without the restriction of cookies. More information about it is available
at
SitePoint.
Geolocation
The Geolocation API is used to obtain the geographical position of the device. This means
it can be used to find the user's exact location and then link to nearby places or measure the
speed at which the user is moving. Because of privacy concerns, permission to use this has
to be granted by the user first.
If geolocation is available it will be a property of the
navigator
object that we met in
a
position
object to a specified function, called
youAreHere()
in the example:
if(navigator.geolocation) {
navigator.geolocation.getCurrentPosition(youAreHere);
}
The
position
object passed to the
youAreHere()
function has a
coords
property
with a
latitude
and
longitude
property, which together give the coordinates of the
device. These coordinates can then be used in conjunction with other applications or web
services (such as a mapping service) to obtain the user's exact location. In this example, we
simply show an alert dialog that displays the user's coordinates:
function youAreHere(position) {
alert("Latitude: " + position.coords.latitude + ",
Longitude:
↵
position.coords.longitude);
}
The
position
object has several other properties that can be used to find out information
about the location and movement of the device:
