Why the js global variable not changed by internal ajax function ?

Question

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JavaScript

var rcode = 0;

//微博认证函数
        function CNY_CheckWeiDo() {            
            

            $.post("do_chy_anthorize.aspx", function (data) {
                var result = eval('(' + data + ')');
                if (result.code == undefined) {                    
                    isLogin = false;
                    rcode = 2;
                    //alert("rcode is 2 :"+rcode);
                }
                if (result.code == 1) {                    
                    isLogin = true;
                    rcode = 1;
                    //alert("rcode is 1 :" + rcode);
                }
                if (result.code == 0) {
                    isLogin = false;
                    rcode = 0;
                    //alert("rcode is 0 :" + rcode);
                    document.location.href = "http://localhost:8870/docheck.aspx" ;
                    
                }
                if (result.code == -2) {                   
                    isLogin = false;
                    rcode = -2;
                    //alert("rcode is -2 :" + rcode);
                    document.location.href =  "http://localhost:8870/docheck.aspx";
                    
                }

                if (result.code == -1) {                    
                    isLogin = false;
                    rcode = -1;
                    //alert("rcode is -1 :" + rcode);
                    document.location.href = "http://localhost:8870/docheck.aspx";                   
                }


            });

            alert("return code :" + rcode);            
            //rcode = 1;

            return rcode;
        }

as the code ,when i alert the value of 'rcode', why the 'rcode' always returns 0 ?

but in the function , when i alert , it's value has changed . can't the global variable be changed in the ajax function ?
who can tell the truth ? thanks

Posted 4-Feb-15 16:09pm

carono

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Comments

ZurdoDev 4-Feb-15 22:33pm

Yes, a global variable can be changed in there.

All you have to do is debug it and you'll see what is happening.

carono 4-Feb-15 22:47pm

yes , i done what you said. but the value is always 0 . in the internal of the function , it is changed , but out of the function , it is 0 again.

ZurdoDev 5-Feb-15 7:32am

Perhaps your page is reloading? That would reset it to 0.

3 solutions

Solution 2

replace alert("return code :" + rcode);

with
setTimeout (function (){ alert (rcode)}, 5000);

here 5000 milliseconds( 5 Seconds) is delay to run alert.

Actually here i am giving 5 seconds delay. So that alert execute after AJAX post can finish its work. Just decrease or increase time delay and see whats happens?

Posted 4-Feb-15 17:19pm

Santosh K. Tripathi

Comments

carono 5-Feb-15 1:47am

thanks S.K. I have solved the issue. with the suggest by DamithSL . thanks for you again.

carono 5-Feb-15 2:03am

yes , S.K , good idea! it is the problem i met . if i set the timer . it returns 0 first time , then it returns the right value at second time , so does the third time ,the fourth time and go on .
but also thank you for your mind.

Santosh K. Tripathi 5-Feb-15 3:17am

welcome :)

Solution 3

thanks you all , it is a issue happened in ajax request.
in the internal of ajax , it requests with synchronous default . by your all 's help and mind , I set the ajax request with asynchronous by using

JavaScript

$.ajaxSetup({
    async : false
});

or such as :

JavaScript

$.ajax({ 
    type : "post", 
    url :'url', 
    data : {jsonparas}, 
    async : false, 
    success : function(data){ 
        //here you can change or assign the global variable
        
     } 
});

luckly , it worked .

thanks!!

Posted 4-Feb-15 19:55pm

carono

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DamithSL · Accepted Answer · 2015-02-04T16:57:00

Solution 1

the reason is when ajax post take time and before that you are returning from the CNY_CheckWeiDo method and having initial value as rcode

Posted 4-Feb-15 16:57pm

DamithSL

Comments

Santosh K. Tripathi 4-Feb-15 23:05pm

Yes you right. yesterday i was facing same problem. After debugging i come to know this behavior of JS.

carono 4-Feb-15 23:10pm

or add the success callback function such as :
$.ajax({
url:'url',
success:function(data){
rcode=1
}
});

carono 4-Feb-15 23:14pm

okey . i will try it by using the $.ajax with the success callback.thanks you guys , S.K & DamithSL .

carono 4-Feb-15 23:07pm

well, thanks damithsl. i think so . do you have some solutions about this issue? cancel the ajax ? use the Synchronous function instead of asynchronous?