Wait until a condition is true?

I’m using navigator.geolocation.watchPosition in JavaScript, and I want a way to deal with the possibility that the user might submit a form relying on location before watchPosition has found its location.

Ideally the user would see a ‘Waiting for location’ message periodically until the location was obtained, then the form would submit.

However, I’m not sure how to implement this in JavaScript given its lack of a wait function.

Current code:

var current_latlng = null;
function gpsSuccess(pos){
    //console.log('gpsSuccess');  
    if (pos.coords) { 
        lat = pos.coords.latitude;
        lng = pos.coords.longitude;
    }
    else {
        lat = pos.latitude;
        lng = pos.longitude;
    }
    current_latlng = new google.maps.LatLng(lat, lng);
}
watchId = navigator.geolocation.watchPosition(gpsSuccess,
                  gpsFail, {timeout:5000, maximumAge: 300000});
$('#route-form').submit(function(event) {
    // User submits form, we need their location...
    while(current_location==null) {
        toastMessage('Waiting for your location...');
        wait(500); // What should I use instead?
    }
    // Continue with location found...
});

Answer

You could use a timeout to try to re-submit the form:

$('#route-form').submit(function(event) {
    // User submits form, we need their location...
    if(current_location==null) {
        toastMessage('Waiting for your location...');
        setTimeout(function(){ $('#route-form').submit(); }, 500); // Try to submit form after timeout
        return false;
    } else {
        // Continue with location found...
    }
});