In Browser location test using navigator.geolocation - example @ https://www.piandmash.com/experiments/location-tracking-in-your-browser/

location.js

var x = document.getElementById("demo");
var watchID = null;
var counter = 0;
function geo_success(position) {
    counter += 1;
    x.innerHTML = "Latitude: " + position.coords.latitude + ", Longitude: " + position.coords.longitude + ", Count: " + counter;
}

function geo_error() {
    x.innerHTML = "Sorry, no position available.";
}

var geo_options = {
    enableHighAccuracy: true,
    maximumAge: 30000,
    timeout: 27000
};

function toggleGeolocation() {
    if ("geolocation" in navigator) {
        if (watchID == null) {
            watchID = navigator.geolocation.watchPosition(geo_success, geo_error, geo_options);
        } else {
            navigator.geolocation.clearWatch(watchID);
            watchID = null;
            x.innerHTML = "Geolocation stopped.";
        }
    } else {
        x.innerHTML = "Geolocation is not supported by this browser.";
    }
}