calculate distance between 2 map points

haversine.js

'use strict';

const toRadians = degrees => (Math.PI / 180) * degrees;
const toDegrees = radians => (180 * radians) / Math.PI;
const earthRadius = 6371e3; // metres

module.exports.getDistance = (ne_lat, sw_lat, ne_lng, sw_lng) => {
	var lat1 = toRadians(ne_lat);
	var lat2 = toRadians(sw_lat);
	var lat_diff = toRadians(sw_lat - ne_lat);
	var lng_diff = toRadians(sw_lng - ne_lng);

	var a =
		Math.sin(lat_diff / 2) * Math.sin(lat_diff / 2) +
		Math.cos(lat1) *
			Math.cos(lat2) *
			Math.sin(lng_diff / 2) *
			Math.sin(lng_diff / 2);
	var c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));

	// return distance between points in meters
	return earthRadius * c;
};