The else block gets executed always before validating the if condition

Question

The else block gets executed always before validating the if condition. The proceedToNextValidation() executed before the Validation(clusterId) gets fully completed its execution. How to wait for the function Validation(clusterId) to be executed fully and then based on its result evaluate the if-else block.

function validateUpgradateStatus()
{
    var target = $("#selectcluster").data("ejDropDownList");
    var clusterId = target.model.itemValue;
    var isValidated = Validation(clusterId);
    if(isValidated )
     Error("error msg");
    else
        proceedToNextValidation();
}
function Validation(id) {
    $.ajax({
        type: "POST",
        url: '@Url.Action("Method", "Controller")',
        data: {
            clusterId: id,
        },
        success: function (response) {
            if (response.isSdkUpgrading) {
                return true;
            }
            else {
                return false;
            }
        }
    });
}

The [jquery's deferred](https://api.jquery.com/jquery.deferred/) may be able to [help](http://stackoverflow.com/a/4874732/4297364) you here. — Moishe Lipsker, Mar 22 '17 at 05:17
You can use jquery .when wait until ajax request complete https://api.jquery.com/jQuery.when/ — D Coder, Mar 22 '17 at 05:20

Robert Schwindaman · Accepted Answer · 2017-03-22T09:28:37.707

Your logic is aimed towards Javascript being a synchronous language. Unfortunately, you have fallen for the same trap as I and many others have when first developing in a language like Javascript.

So your Validation() function sends an AJAX request, and then ON SUCCESS (aka: the HTTP request completed successfully), your ANONYMOUS SUCCESS CALLBACK FUNCTION returns true or false depending on the result. The key here is that the Validation() function is not returning true or false in the same way. Immediately, the Validation function actually returns 'null'. It doesn't wait for the AJAX (HTTP) request to complete.

The fix here is that you need to:

Option #1: Pass Validation a 2nd parameter called callback, which is a function. You then set the success AJAX property to your parameter callback as so:

var callback = function(response){
    if(response.isSdkUpgrading)Error("error msg");
    else proceedToNextValidation();
}

function Validation(id, callback){
    $.ajax({
        type: "POST",
        url: '@Url.Action("Method", "Controller")',
        data: {clusterId: id},
        success: callback
    });
}

Option #2: Move your logic that needs to wait for the AJAX (HTTP) request to complete into your anonymous success callback as so:

function Validation(id){
    $.ajax({
        type: "POST",
        url: '@Url.Action("Method", "Controller")',
        data: {clusterId: id,},
        success: function(response){
            if(response.isSdkUpgrading)Error("error msg");
            else proceedToNextValidation();
        }
    });
}

Hope this helps.

score 2 · Answer 2 · answered Mar 22 '17 at 05:19

You should ideally place your code inside the callback then...

function validateUpgradateStatus()
{
  var target = $("#selectcluster").data("ejDropDownList");
  var clusterId = target.model.itemValue;
  Validation(clusterId);
}
function Validation(id) {
   $.ajax({
     type: "POST",
     url: '@Url.Action("Method", "Controller")',
     data: {
        clusterId: id,
    },
    success: function (response) {
        if (response.isSdkUpgrading) {
             Error("error msg");
        }
        else {
            proceedToNextValidation();
        }
    }
 });
}

While this is certainly an option, OP's case of Validation (dynamic verification of fields/etc) may require a different callback for each different type of "Validation". A callback parameter is a more elegant solution here in my opinion. — Robert Schwindaman, Mar 22 '17 at 09:31

score -1 · Answer 3 · answered Mar 22 '17 at 05:18

-1

if(!isValidated)
     Error("error msg");
    else
        proceedToNextValidation();

If ! not Validated then you will get the error, Else proceedToNextValidation();

answered Mar 22 '17 at 05:18

Ryan Dooley

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How to wait for the function Validation(clusterId) to be executed fully and then based on its result evaluate the if-else block. – Kumaran Raj K Mar 22 '17 at 05:20

The else block gets executed always before validating the if condition

3 Answers3