"Geolocation": Chapbook (v1.0.0)

Summary

Many browsers allow access to the current location through the Geolocation property and associated functions. This functionality is subject to the user agreeing to allow access. Until the functionality is unlocked, or if the user declines, default values will be returned.

Functionality availability and their results should always be tested against other location services or information. Most browsers will return results through the fastest and sometimes least-accurate methods possible.

In this example, the [JavaScript] modifer is used to test for, run, and show data using an alert() from the JavaScript functions.

Live Example

Download: Live Example

Twee Code

:: StoryTitle
Chapbook: Geolocation

:: UserScript[script]
(function () {

    window.geolocation = {

        available: function() {
            return ("geolocation" in navigator 
                && typeof navigator.geolocation.getCurrentPosition === "function");
        },
        getLocation: function() {

            // Create initial values
            var location = { latitude : 0, longitude : 0 };

            // Create success callback to store values
            var    positionSuccess = function (position) {

                location.latitude = position.coords.latitude;
                location.longitude = position.coords.longitude;

            };

            // Create error callback
            var positionError = function (error) {
                /* Code that handles errors */
            };

            // Create initial options
            var positionOptions = {
                timeout: 31000, 
                enableHighAccuracy: true,
                maximumAge : 120000
            };


            // Ask for location based on callbacks and options
            navigator.geolocation.getCurrentPosition(
                positionSuccess,
                positionError,
                positionOptions
            );

            // Return location found
            // If not location, will return initial (0,0) values
            return location;

        },
        approximateLocation: function (a, b, allowedDiff) { 
            // allowedDiff must always be > 0
            if (a === b) { // handles various "exact" edge cases
                return true;
            }

            allowedDiff = allowedDiff || 0.0005;

            return Math.abs(a - b) < allowedDiff;
        }

    };

}());

:: Start
[[GeoLocation]] 

:: GeoLocation
[JavaScript]
if(window.geolocation.available() ) {
    var geolocation = window.geolocation.getLocation();    
    alert("Latitude: " + geolocation.latitude + " Longitude:" + geolocation.longitude);
}
[continued]

Download: Twee Code

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