Question

I’m just trying to get variables out of the geolocation.getCurrentPosition function from HTML5. However, I’m having a lot of difficulties getting my variables to be defined outside of the function.

The function works using the code below:

<script>
var latitude;
var longitude;
var accuracy;
var altitude;
var altitudeAccuracy;
var heading;
var speed;

if (navigator.geolocation){
  navigator.geolocation.getCurrentPosition(  
    function (position) {
      latitude = position.coords.latitude;
      longitude = position.coords.longitude;
      alert(longitude)
      accuracy = position.coords.accuracy;
      altitudeAccuracy = position.coords.altitudeAccuracy;
      heading = position.coords.heading;
      speed = position.coords.speed;
    }
  );
}

// alert(latitude);

Here I see the alert(longitude) return a numerical value. However when I comment that line out, and uncomment alert(latitude) — I get an “undefined” alert.

Any help would be greatly appreciated! Thanks.

Answer 1

Because getCurrentPosition is an asynchronous call.

You need to wait for the callback to fire before you can access the values it retrieves.

function nextStep(){
    alert(latitude);
}

navigator.geolocation.getCurrentPosition(  
    function (position) {
      latitude = position.coords.latitude;
      longitude = position.coords.longitude;
      alert(longitude)
      accuracy = position.coords.accuracy;
      altitudeAccuracy = position.coords.altitudeAccuracy;
      heading = position.coords.heading;
      speed = position.coords.speed;
      nextStep();
    }
);