return function value from $.post callback

Question

js:

 function verificaExistPed(numped){
        var valida;
        jQuery.post("procedures/class_oc.php", // ajax post
            {
                cache      : false,
                checkYear  : true,
                numped     : numped
            },
            function(data)
            {
                if(data === "s"){
                    valida = true;
                }else{
                    valida = false;
                }
            }
        )
        return valida;
  }

and, calling the function in another place, should return valida result inside variable check, in my case, true or false.

var check = verificaExistPed('".$numped."');
alert(check); // always undifined

but, always undefined.

how can i set valida to true or false from a $.post callback ?

possible duplicate of [JavaScript asynchronous return value / assignment with jQuery](http://stackoverflow.com/questions/7779697/javascript-asynchronous-return-value-assignment-with-jquery) — Felix Kling, Dec 07 '11 at 11:15

score 2 · Answer 1 · answered Dec 07 '11 at 11:15

2

It's because handler are invoked asinchronously after your functon invoked. So you synchronously request for it, like:

function test() {
    var html = $.ajax({
    url: "procedures/class_oc.php",
       async: false // <-- heres the key !
    }).responseText;

    return html;
}

answered Dec 07 '11 at 11:15

Samich

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Making synchronous calls is a bad idea in general, as it can freeze the browser. – Felix Kling Dec 07 '11 at 11:16
Yep, but in this case if OP need a result of the function with ajax request it's only way to do it. – Samich Dec 07 '11 at 11:17
1

No it's not the only way. He should pass a callback instead and put all the logic that needs this result into the callback. It's pretty straightforward with jQuery's deferred objects (see the duplicate question I linked to). – Felix Kling Dec 07 '11 at 11:18
This will freeze the browser (atleast IE) – Abdul Munim Dec 07 '11 at 11:18
If you passing the callback it's already not a result of invoking, it will invoke your callback after ajax call and it can be not a case in OP situation if he needs this value just after calling. – Samich Dec 07 '11 at 11:20
That's how you are going to design to work along async calls. Hampering UX is the worst thing ever. – Abdul Munim Dec 07 '11 at 11:34

score 1 · Accepted Answer · edited Feb 14 '12 at 09:22

1

You cannot return from as jQuery.post is an asynchronous call. You have to rely on a callback function in order to get the response from server. Try this:

 function verificaExistPed(numped, isValidCallback){
        jQuery.post("procedures/class_oc.php", // ajax post
            {
                cache      : false,
                checkYear  : true,
                numped     : numped
            },
            function(data)
            {
                isValidCallback(data === "s");
            }
        )
  }

USAGE:

verificaExistPed('".$numped."', function(isValid) {
   alert(isValid); //returns true or false
});

edited Feb 14 '12 at 09:22

T.J. Crowder

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answered Dec 07 '11 at 11:17

Abdul Munim

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@T.J.Crowder thanks, I should have done some modifications to RicardoArruda code – Abdul Munim Feb 14 '12 at 06:37
@T.J.Crowder surely I could :) better be late than never :) – Abdul Munim Feb 14 '12 at 07:43

return function value from $.post callback

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