如何在google应用程序脚本中的函数之间共享地图

var map;

function createMap() {
  map = new google.maps.Map(document.getElementById('map'), {
    center: {lat: -34.397, lng: 150.644},
    zoom: 8
  });
}

function addMarker() {
  var marker = new google.maps.Marker({
    position: {lat: -34.397, lng: 150.644},
    map: map,
    title: 'Marker'
  });
}

function createMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    center: {lat: -34.397, lng: 150.644},
    zoom: 8
  });
  
  addMarker(map);
}

function addMarker(map) {
  var marker = new google.maps.Marker({
    position: {lat: -34.397, lng: 150.644},
    map: map,
    title: 'Marker'
  });
}

function createMap() {
  var map = new google.maps.Map(document.getElementById('map'), {
    center: {lat: -34.397, lng: 150.644},
    zoom: 8
  });
  
  return function() {
    var marker = new google.maps.Marker({
      position: {lat: -34.397, lng: 150.644},
      map: map,
      title: 'Marker'
    });
  };
}

var addMarker = createMap();