JavaScript (Pure) function to calculate the destination point by start point (latitude, longitude [numeric]), bearing (numeric degrees) and distance (km).

calculate destination latitude and longitude by starting latitude, longitude, bearing, and distance.js

/*!
 * JavaScript　(Pure) function to calculate the destination point by start point (latitude, longitude [numeric]), bearing (numeric degrees) and distance (km).
 *
 * Optimized from https://stackoverflow.com/a/2637079/6160436
 */
(function(){
  function toRad(val) {
    return val * Math.PI / 180;
  };

  function toDeg(val) {
    return val * 180 / Math.PI;
  };

  /**
   * calculate
   * @param {Decimal} startLat - Starting latitude
   * @param {Decimal} startLng - Starting longitude
   * @param {Number}  brng     - Bearning: From 0=North
   * @param {Number}  dist     - Distance in kilometers
   *
   * @return {Object} Return {lat: Decimal(), lng: Decimal()}
   */
  window.calcDestLatlng = function(startLat, startLng, brng, dist) {
    dist = dist / 6371;
    brng = toRad(brng);

    startLat = toRad(startLat);
    startLng = toRad(startLng);

    var destLat = Math.asin(Math.sin(startLat) * Math.cos(dist) +
      Math.cos(startLat) * Math.sin(dist) * Math.cos(brng));

    var destLng = startLng + Math.atan2(Math.sin(brng) * Math.sin(dist) *
      Math.cos(startLat),
      Math.cos(dist) - Math.sin(startLat) *
      Math.sin(destLat));

    if (isNaN(destLat) || isNaN(destLng)) return null;

    return {
      lat: toDeg(destLat),
      lng: toDeg(destLng)
    };
  };
})();