loll

gistfile1.txt

function calculateDistance(lat1, lon1, lat2, lon2) {
  var R = 6371; // km
  var dLat = (lat2 - lat1).toRad();
  var dLon = (lon2 - lon1).toRad(); 
  var a = Math.sin(dLat / 2) * Math.sin(dLat / 2) +
          Math.cos(lat1.toRad()) * Math.cos(lat2.toRad()) * 
          Math.sin(dLon / 2) * Math.sin(dLon / 2); 
  var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a)); 
  var d = R * c;
  return d;
}
Number.prototype.toRad = function() {
  return this * Math.PI / 180;
}