Question

I have created this script with the help of the Haversine formula, the problem is that it keeps directing me to the first location on the array, no matter how many time I swap them about. Any ideas?

var locations = new Array(
  Array("Brighton", 50.82253, -0.137163),
  Array("Chichester", 50.83761, -0.774936),
  Array("Portsmouth", 50.8166667, -1.0833333),
  Array("Worthing", 50.81787, -0.372882)
);

function deg2rad(degrees){
    radians = degrees * (Math.PI/180);
    return radians;
}

function haversine(lat1,lon1,lat2,lon2) {
    deltaLat = lat2 - lat1;
    deltaLon = lon2 - lon1;
    earthRadius = 3959; // In miles (6371 in kilometers)
    alpha = deltaLat/2;
    beta = deltaLon/2;
    a = Math.sin(deg2rad(alpha)) * Math.sin(deg2rad(alpha)) 
      + Math.cos(deg2rad(lat1)) * Math.cos(deg2rad(lat2)) 
      * Math.sin(deg2rad(beta)) * Math.sin(deg2rad(beta));
    c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1-a));
    distance = earthRadius * c;
    return distance.toFixed(2);
}

function locationSuccess(position) {

    var places = new Array();
    var userLatitude = position.coords.latitude;
    var userLongitude = position.coords.longitude;

    for(var i=0;i<locations.length;i++) {
        places.push(haversine(
          userLatitude,
          userLongitude,
          locations[i][1],
          locations[i][2]
        ));
    }

    var sorted = places.sort(); // Sort places from low to high 

    /*
    alert(places); // Listed distances unordered
    alert(sorted); // Listed distances in order
    alert(sorted[0]); // Nearest city distance
    */

}

function locationFailed() {
    // Change me to a better error message
    alert("Ooops, we couldn't find you!"); 
}

// Get user's physical location
navigator.geolocation.getCurrentPosition(locationSuccess, locationFailed);

Answer 1

You’re not sorting the array of locations, only the array of distances.

You should drop the distance into the locations array (i.e. as the fourth member of each element):

for(var i = 0; i < locations.length; ++i) {
    var l = locations[i];
    l[3] = haversine(userLatitude, userLongitude, l[1], l[2]);
}

and then use a “comparator” function that looks at that distance field:

locations.sort(function(a, b) {
    return (a[3] < b[3]) ? -1 : ((a[3] > b[3]) ? 1 : 0);
});