Question

My function fetches if the user is banned and i want to return a variable that determines if a popup displays; but as I’ve found out you can’t return a variable from a getJSON function.

 function fetchban() {
    $.getJSON('/fetchban.php',function(data) {

        if(data==0) {

            var banned =  data;
        } else {
            $.each(data,function(index,result) {
            $('#ban-prompt').html(result);
            $('.popup-background').show();
            $('#ban-container-2').show();
            });
        }

    });

    return banned;
}

$('.button').click(function() {
var banned = fetchban();

if(banned==0) {

//display-popup

}

});

There are alot of lines i call the fetchban function, so i would prefer the getJSON in a function. What is the solution?

Answer 1

There are two problems with your function.

The first, and the most significant, is that it assumes that getJSON is synchronous. It is asynchronous by default, meaning it’s impossible for fetchban to return a value based on the data retrieved. Instead, fetchban should accept a callback it calls with the result.

The second (which will go away anyway once you fix the first), is that you’re trying to return a variable from fetchban that isn’t declared (because you declare it inside your getJSON success handler).

So you’d change fetchban to look something like:

function fetchban(callback) {
    $.getJSON('/fetchban.php',function(data) {
        var banned;

        // ...figure out what `banned` should be from the `data`,
        // I'm afraid I couldn't make sense of the code, looked
        // like it always set `banned` to 0.

        // Call the callback with the result
        callback(banned);
    });
}

And then instead of:

$('.button').click(function() {
    var banned = fetchban();

    if(banned==0) {
        //display-popup
    }
});

do this:

$('.button').click(function() {
    fetchban(function(banned) {
        if(banned==0) {
            //display-popup
        }
    });
});

…or much better, fetch it earlier so you already have that information when the click arrives. Users don’t like delays when they click, and even the best case on a web round-trip is noticeable to human beings.