Google Maps multiple destinations sorted by shortest path

gmaps.js

require('es6-promise').polyfill();

var request = require('request');


const API_KEY = process.env.GOOGLE_MAPS_API_KEY || '';

var places = [
  'steins, mountain view, CA',
  'st. stephens green, mountain view, CA',
  'shana thai, mountain view, CA',
  'beefys cabin, sunnyvale, CA',
];
var promises = [];


var _fetch = function (data) {
  return new Promise(function (resolve, reject) {
    request.get(data, function (err, response) {
      if (err) {
        reject(err);
      } else {
        if (response.statusCode !== 200) {
          return reject(new Error('Unexpected response code: ' +
                                  response.statusCode));
        }

        resolve(response);
      }
    });
  });
};



function url(name, data) {
  switch (name) {
    case 'directions':
      if (Array.isArray(data)) {
        data = {waypoints: data};
      }
      if (!data.mode) {
        data.mode = 'walking';
      }

      return 'https://maps.googleapis.com/maps/api/directions/json?origin=' +
        encodeURIComponent(data.waypoints[0]) +
        '&destination=' + encodeURIComponent(data.waypoints[data.waypoints.length - 1]) +
        '&waypoints=optimize:true|' + data.waypoints.map(encodeURIComponent).join('|') +
        '&optimizeWaypoints=true&mode=' + data.mode;

    case 'geocode':
      if (typeof data === 'string') {
        data = {address: data};
      }

      return 'https://maps.google.com/maps/api/geocode/json?key=' + API_KEY +
        '&address=' + encodeURIComponent(data.address);
  }
}



places.forEach(function (place) {

  promises.push(
    _fetch({
      url: url('geocode', place),
      json: true
    }).then(function (response) {
      return response.body;
    })
  );

});


Promise.all(promises).then(function (addresses) {

  var coords = addresses.map(function (address) {
    return [address.results[0].geometry.location.lat,
            address.results[0].geometry.location.lng].join(',');
  });

  return _fetch({
    url: url('directions', coords),
    json: true
  }).then(function (response) {
    return response.body;
  });

}).then(function (data) {

  var waypointOrder = data.routes[0].waypoint_order;

  var placesOrdered = waypointOrder.map(function (orderIdx) {
    return places[orderIdx];
  });

  return placesOrdered;

})
.then(console.log)
.catch(console.error);

i dont want it in shortest path i want same like normal as per the priority set in path

Can you please explain the code not necessarily every line, but comment on what each chunk of code does..