sample.js

var zimride = require('./zimride');

var pointA = {lat: 55.157199, lng: 61.364264}; 
var pointB = {lat: 55.15791, lng: 61.38864}; 
var pointC = {lat: 55.153472, lng: 61.364779}; 
var pointD = {lat: 55.153864, lng: 61.381688}; 

console.log(zimride.getMinDetourDistance(pointA, pointB, pointC, pointD));

task.js

var R = 6371;

Number.prototype.toRad = function () {
	return this * Math.PI / 180;
}

function getDistance(point1, point2) {
	lat1 = point1.lat.toRad();
	lon1 = point1.lng.toRad();
	lat2 = point2.lat.toRad();
	lon2 = point2.lng.toRad();

	return Math.acos(Math.sin(lat1)*Math.sin(lat2) + 
		   Math.cos(lat1)*Math.cos(lat2) *
		   Math.cos(lon2-lon1)) * R;
}

/*
	driver1 should get from A to B
	driver2 should get from C to D
	so either driver1 will pick driver2 - route ACDB
	or driver2 will pickup driver1 - route CABD
	since both route have common legs AC and BD, to get minimal detour distance we should compare AB and CD legs
*/ 
 
exports.getMinDetourDistance = function(pointA, pointB, pointC, pointD) {
	var ab = getDistance(pointA, pointB);
	var cd = getDistance(pointC, pointD);
	
	return Math.min(ab,cd) + getDistance(pointA, pointC) + getDistance(pointB, pointD);	
}