如何在Javascript中的异步函数内部分配全局变量？

Question

控制台记录lat会返回undefined ，而我想为其分配position.coords.latitude的值。 问题是什么？

 $(document).ready(function(){ var lat, lon; if (navigator.geolocation) { navigator.geolocation.getCurrentPosition(function(position) { lat=position.coords.latitude; lon=position.coords.longitude; }); console.log(lat); } }); 

Answer 1

您无法登录那里，您必须需要回调函数才能实现目标

<script>
  var x = document.getElementById("demo");
  function getLocation() {
    if (navigator.geolocation) {
      navigator.geolocation.getCurrentPosition(showPosition);
    } else {
      x.innerHTML = "Geolocation is not supported by this browser.";
   }
 }
function showPosition(position) {
  console.log("Latitude: " + position.coords.latitude +" Longitude: "          + position.coords.longitude)
  x.innerHTML = "Latitude: " + position.coords.latitude + 
  "<br>Longitude: " + position.coords.longitude; 
}
</script>

Answer 2

使用回调函数$（document）.ready（function（）{var lat，lon;

  if (navigator.geolocation) {
     navigator.geolocation.getCurrentPosition(function(position) {
        lat=position.coords.latitude;
        lon=position.coords.longitude;
        callbackFunction();
     });
   }

   function callbackFuncton(){
      console.log(lat);
      //you can use your lat and lon here
   }
});