Set of functions for determining the distance between 2 lat,lng points

distance_functions.js

var radiusOfEarth = 6378100.0;

function deg2rad(deg) {
  return deg * (Math.PI / 180);
}

function rad2deg(rad) {
  return rad * (180 / Math.PI);
}

function computeDistanceBetween(from, to) {
  return distance(from.lat, from.lng, to.lat, to.lng);
}

function distance(lat1, lng1, lat2, lng2) {
  return ( radiusOfEarth * Math.acos( Math.cos( deg2rad(lat1) ) * Math.cos( deg2rad(lat2) ) * Math.cos( deg2rad(lng2) - deg2rad(lng1) ) + Math.sin( deg2rad(lat1) ) * Math.sin( deg2rad(lat2) ) ) );
}