JavaScript Global Variable is undefined

Question

I have already read Surprised that global variable has undefined value in JavaScript.

But my problem is differ because I have not created same variable name inside..

$(document).ready(function() {
    var all_ap;
    var url = "http://localhost/example/php-code/json.php";
    $.getJSON(url, function(result) {
        all_ap = result;
        console.log(result);
    });
    console.log(all_ap);
});

These are the console results.

undefined
(6) [{…}, {…}, {…}, {…}, {…}, {…}]

Seems like console.log(all_ap); works before console.log(result); according to results of above.

Why is that? How should I make all_ap variable works?

It's undefined because you are trying to use it *before* it's been assigned any value. `$.getJSON` is asynchronous. — David, Sep 26 '17 at 12:40

score 0 · Answer 1 · answered Sep 26 '17 at 12:40

0

Because $.getJSON is asynchronous function thus callback provided to it gets called after it's finished in the future. That's why your console.log(all_app) gets called first because it's called synchronously just after $.getJSON.

answered Sep 26 '17 at 12:40

lukaleli

3,427
3
22
32

Thanks for the answer. Can you please tell me that how I modify above code to getJSON result to global variable? I read https://stackoverflow.com/questions/14220321/how-do-i-return-the-response-from-an-asynchronous-call. But It is hard to understand it. Can you please edit your answer how I correct my issuie? – I am the Most Stupid Person Sep 27 '17 at 04:16

JavaScript Global Variable is undefined

1 Answers1