Find the closest location

main.js

var cities = [
  {
    name: 'berlin',
    latitude: '52.5167',
    longitude: '13.3833',
  },
  {
    name: 'athena',
    latitude: '37.9667',
    longitude: '23.7167',
  }
];

function pythagorasEquirectangular( lat1, lon1, lat2, lon2 ) {
  lat1 = Deg2Rad(lat1);
  lat2 = Deg2Rad(lat2);
  lon1 = Deg2Rad(lon1);
  lon2 = Deg2Rad(lon2);
  var R = 6371; // km
  var x = (lon2-lon1) * Math.cos((lat1+lat2)/2);
  var y = (lat2-lat1);
  var d = Math.sqrt(x*x + y*y) * R;
  return d;
}

// Convert Degress to Radians
function Deg2Rad( deg ) {
  return deg * Math.PI / 180;
}

function nearestCity( latitude, longitude )
{
  var mindif=99999;
  var closest;

  for (index = 0; index < cities.length; ++index) {
    var dif =  pythagorasEquirectangular(latitude, longitude, cities[index].latitude, cities[index].longitude);
    if (dif < mindif) {
      closest=index;
      mindif = dif;
    }
  }
  return cities[closest];
}