HERE Maps for Javascript API: Calculate closest routing maneuver to the current geo position

Question

I am using HERE Maps JS API. I am able to request a route based on start and end positions. Now, the route shows all the maneuvers in a single response like an array as shown in the figure below. How can I figure out which maneuver to select based on the latitude and longitude of current position?

Answer 1

You should loop over maneuver array and check the distance between the maneuver's position and desired geo location using H.geo.Point#distance method, something like this:

// ...
// assuming we're in calculateRoute response callback
// and result is callback's parameter

var maneuver = result.response.route[0].leg[0].maneuver,
    testPosition = {lat: 50, lng: 13},
    closestManeuver,
    closestManeuverPoint,
    minDistance = Infinity;

// calculate the closest maneuver
maneuver.forEach(function(man) {
  let currManeuverPoint = new H.geo.Point(
    man.position.latitude, 
    man.position.longitude
  ),
  currDistance = currManeuverPoint.distance(testPosition);

  if (currDistance < minDistance) {
    minDistance = currDistance;
    closestManeuver = man;
    closestManeuverPoint = currManeuverPoint;
  }
});

console.log('closest maneuver (%s m) is at: {lat: %s, lng: %s}: \n %s', Math.round(minDistance), closestManeuverPoint.lat, closestManeuverPoint.lng, closestManeuver.instruction);

I created simple jsfiddle example which shows a route in Berlin and calculates closest maneuver point (rendered as marker) on each mouse click. Check the console log for detailed information about closest maneuver point.