javascript - Facing trouble with global variable in JS

Question

Following code is to track user location,

var curr_loc; //global varible
function displayLocation(loc) {
    currLat = loc.coords.latitude;
    currLon = loc.coords.longitude;
    curr_loc = currLat + "," + currLon;
    alert(curr_loc); //Displaying latitude and longitude values 
}

function foo() {
    navigator.geolocation.getCurrentPosition(displayLocation);
    alert(curr_loc); //undefined
}
foo();

How can I access location values in foo method.

Answer 1

navigator.geolocation.getCurrentPosition(displayLocation)ポジションが確立される前に戻りdisplayLocation、将来のポジションが利用可能になったときに呼び出されます。まだ呼び出されていないため、返品curr_loc後しばらくの間は未定義です。navigator.geolocation.getCurrentPosition()displayLocation