Global variable in JavaScript not set when using getJSON?

Question

Here's my code. If i check "pranks" variable by "google inspector" all works fine. But the "alert" on the last line show a 0-size array! I mucking with local/global variables?

<script type="text/javascript">
(function() { 

 pranks = [];

function getAllPranks(){


    $.getJSON('list.json', function(data) {

      $.each(data['pranks'], function(key, val) {
        pranks.push(val);
      });

    });

}

 $(document).ready(function(){


    getAllPranks();

    alert(pranks.length);

 });


 }());
 </script>

Please search for "jquery return value from ajax". The answer will be there. — user166390
– user166390, Commented May 4, 2012 at 21:41
stackoverflow.com/questions/2960417/… , stackoverflow.com/questions/4158865/… , stackoverflow.com/questions/3537434/… — user166390
– user166390, Commented May 4, 2012 at 21:45
possible duplicate of How can I return a variable from a $.getJSON function — user166390
– user166390, Commented May 4, 2012 at 21:46

Tim B James · Accepted Answer · 2012-05-04 21:34:22Z

3

Change it to:

$.getJSON('list.json', function(data) {
  $.each(data['pranks'], function(key, val) {
    pranks.push(val);
  });
  alert(pranks.length); /* pranks has data now */
});

answered May 4, 2012 at 21:34

Tim B James

20.4k4 gold badges77 silver badges108 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Florian Margaine · Accepted Answer · 2012-05-04 21:49:36Z

1

Taking your code:

<script type="text/javascript">
(function() { 
    function getAllPranks( callback ) {
        $.getJSON('list.json', function(data) {
            $.each(data['pranks'], function(key, val) {
                pranks.push(val);
            });
            callback( pranks );
        });
    }

    $(document).ready(function(){
        getAllPranks( function( pranks ) {
            alert(pranks.length);
        } );
    });
}());
</script>

$.getJSON is asynchronous. This means the callback function (function(data)) is executed once the result comes back. When you execute alert(pranks.length), the function has not executed because the response hasn't come back at this moment.

answered May 4, 2012 at 21:49

Florian Margaine

61.2k15 gold badges94 silver badges120 bronze badges

Collectives™ on Stack Overflow

Global variable in JavaScript not set when using getJSON?

2 Answers 2

Comments

Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related