Saving variables outside of navigator.geolocation.getCurrentPosition? (javascript)

问题

I'm trying to play with the scope of js to pull a variable out of navigator.geolocation.getCurrentPosition

var lat;
function callback (position) {
    lat = position.coords.latitude;
}
navigator.geolocation.getCurrentPosition(callback,fail,{timeout:10000});
// after getCurrentPosition succeeds
alert(lat); // this alerts null

The above code cannot store position.coords.latitude in the lat variable because of the scope. Is there a way to do this?

回答1:

You have to remember the async\ajax nature.

this is the execution order of your code:

var lat;
alert(lat); // this alerts null
navigator.geolocation.getCurrentPosition(callback,fail,{timeout:10000});
function callback (position) {
    lat = position.coords.latitude;
}

This why you get null. async!, async! :)

回答2:

You can save your Position variable to input hidden field on document ready. After that, you can use jQuery to get back Geolocation value

Javscript:

<script>
var lat;
alert(lat); // this alerts null
navigator.geolocation.getCurrentPosition(callback,fail,{timeout:10000});
function callback (position) {
    jQuery('#pos_lat').val(position.coords.latitude);
}
</script>

HTML:

    <input hidden id='pos_lat' value='' /> 
    //value = position latitude on load

To get back value:

jQuery('#pos_lat').val();

来源：https://stackoverflow.com/questions/9935059/saving-variables-outside-of-navigator-geolocation-getcurrentposition-javascrip