Question

javascript snippet :

<script type="text/javascript">
$(document).ready(function() {

    setInterval(function() {
        $.getJSON('notif.php', function(data) {
            my_var = '123';
        });
        alert("my var =" + my_var);
    }, 2000);

});    
</script>

in chrome and FF console, my_var shows to be undefined, but its value is shown on the alertbox. if undefined , then how is its val

What is the explanation ?

Answer 1

getJSON in jquery is by default asynch call so the alert("my var =" + my_var); will be executed without waiting for the response of the ajax call.

move the alert inside callback function like

setInterval(function() {
    $.getJSON('notif.php', function(data) {
        my_var = '123';
        alert("my var =" + my_var);
    });
}, 2000);