Haversine - Straight Line Distance Between Two Sets of Geographical Coordinates (Latitude, Longitude)

haversine.js

// see the Haversine formula description here
// https://community.esri.com/t5/coordinate-reference-systems/distance-on-a-sphere-the-haversine-formula/ba-p/902128
function haversine(coord1, coord2){
  // radius of earth in meters
  const R = 6371000;

  // convert latitude degrees to radians
  const phi_1 = Math.radians(coord1.latitude);
  const phi_2 = Math.radians(coord2.latitude);

  // delta being the "difference" between the latitudes and longitudes of each coordinate set expressed
  // in radians
  const delta_phi = Math.radians(coord2.latitude - coord1.latitude);
  const delta_lambda = Math.radians(coord2.longitude - coord1.longitude);

  // sin²(φB - φA/2) + cos φA * cos φB * sin²(λB - λA/2)
  const a = Math.sin(delta_phi/2.0)**2 + Math.cos(phi_1) * Math.cos(phi_2) * Math.sin(delta_lambda/2.0)**2;

  // 2 * atan2( √a, √(1−a) )
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

  const meters = R * c;
  const kilometers = meters / 1000.0;
  const miles = kilometers / 1.609344;

  return { meters, kilometers, miles};
}