JavaScript variable undefined outside ajax

Question

im making a simple script so a piece of code can run in a loop.

 var num_rows_php;
    var num_rows_sessions_php;
    var num_rows_session_php_teste;

    $.ajax({
    url: 'verify_num_rows.php',
    success: function(){
    num_rows_php = "<?php echo $my_num_rows; ?>";
    num_rows_session_php = "<?php echo $_SESSION['transaction_count']; ?>";
    num_rows_session_php_teste = "<?php echo $_SESSION['teste_num']; ?>";
    alert('num_rows_session' + num_rows_session_php);
    alert('num rows session php teste' + num_rows_session_php_teste);
    },

    });

    alert('teste fora do ajax' + num_rows_session_php_teste);

I only posted the relevant part here, where my problem is. So i create the variables outside the ajax function, so i can update them inside the ajax function. this piece of code is running every 5 seconds, so even if the ajax call isn't made first, the variables should update anytime. My problem is, when i do the Alertsinside the ajax function, the values are correct, but the alert outside the ajax function says the variable is undefined. alert('teste fora do ajax' + num_rows_session_php_teste); is undefined, even after the code runs like 10 times. Why is this ?

EDIT :

i tried this:

$.ajax({
            url: 'verify_num_rows.php',
            success: function(){
            num_rows_php = "<?php echo $my_num_rows; ?>";
            num_rows_session_php = "<?php echo $_SESSION['transaction_count']; ?>";
            num_rows_session_php_teste = "<?php echo $_SESSION['teste_num']; ?>";
            alert('num_rows_session' + num_rows_session_php);
            alert('num rows session php teste' + num_rows_session_php_teste);
            if (num_rows_session_php_teste != num_rows_session_php)
            {
              alert(num_rows_session_php_teste);
                //   alert (num_rows_session_php);
              $('#tbody').load('table_body.php')
              $('#myfooter').load('myfooter.php')
              $('#my-list').load('mylist.php')



        }
        },

        });

everything inside ajax success function and the variable is undefined in the moment of the alert.

That is because of Asynchronus calls. Have a look on Sync vs Async — Navaneeth
– Navaneeth, Commented Jul 12, 2016 at 8:59
that depends on context. If the code you gave was wrapped in a function, then everytime a new num_rows_session_php_teste variable is created. so undefined everytime — Navaneeth
– Navaneeth, Commented Jul 12, 2016 at 9:02

apelidoko · Accepted Answer · 2017-08-25 06:44:17Z

1

try adding async: false on your ajax function,

$.ajax({
     url: 'verify_num_rows.php',
     async: false,
     success: function(){
     }
})

answered Aug 25, 2017 at 6:44

apelidoko

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Comments

kawadhiya21 · Accepted Answer · 2016-07-12 09:02:22Z

0

You cannot expect $.ajax to assign value to num_rows_session_php_teste. Since JS is async in nature, alert might get invoked before $.ajax takes place. Hence it is possible that num_rows_session_php_teste is undefined when accessed from alert.

answered Jul 12, 2016 at 9:02

kawadhiya21

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8 Comments

Susheel Singh Over a year ago

This could be a comment not an answer

Pedro Costa Over a year ago

hm, even inside the ajax code itself, that can happen ?

kawadhiya21 Over a year ago

No, not inside the code. Because the $.ajax gets called, then goes into success where the variables get assigned first. So inside ajax block, it would work well but not outside.

kawadhiya21 Over a year ago

hmm this would do the job. Correct implementation !

Pedro Costa Over a year ago

hm now the variables have no value at all, not undefined.

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