Calculate Distance from 2 Coordinates

harvesine.js

function harvesine(pta, ptb) {
  
  const [lat1, lon1] = pta.split(',')
  const [lat2, lon2] = ptb.split(',')
  
  // convert to radians
  const rad1 = (lat1 * Math.PI) / 180;
  const rad2 = (lat2 * Math.PI) / 180;
  const dLat = ((lat2 - lat1) * Math.PI) / 180;
  const dLon = ((lon2 - lon1) * Math.PI) / 180;

  // Haversine formula
  const a =
    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(rad1) * Math.cos(rad2) * Math.sin(dLon / 2) * Math.sin(dLon / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  const R = 6371; // Earth's radius in kilometers

  // return distance in kilometers
  return Math.round(R * c) + ' Km';
  
}

// Usage:
// var p1 = '52.518611,13.408056'
// var p2 = '51.507222,-0.1275'

// console.log(harvesine(p1, p2))