How to stop submission of a form based on the value returned by an asynchronous callback ?

[PriyaVerma]

I have written following code in Catalog Client Script. I want to stop submit record based on the value returned by ValidateAttachment. If ValidateAttachment returns false, I am using return false (to stop submit record). But this is not working as the issue is: Script continues to submit record before the callback returns response. 

 function onSubmit()  

{

      var id = '50eebf051bff35501738eb17ec4bcb59';

    // var id = g_form.getUniqueValue();

    // AJAX call to the server-side script include

    var ga = new GlideAjax('NGRPPortalUtilAjax');

    ga.addParam('sysparm_name', 'validateAttachment');

    ga.addParam('sysparm_app_id', id);

    ga.getXML(ValidateAttachment);

}

function ValidateAttachment(response)

{

    var answerFromXML= response.responseXML.documentElement.getAttribute("answer");

    var result = JSON.parse(answerFromXML);

    if(result=='true')

    {

        alert('Valid Insert' + result);

        return true;

    }

    else

    {

         alert("Please upload valid format" + result);

         return false;

    }

}

[SanjivMeher]

I dont think getXML will work. Because it is asynchronous.

You need to use getXMLWait instead.

[PriyaVerma]

getXMLWait  does not work on Service Portal. 

[SanjivMeher]

There is an alternate solution provided in the below article, which may work for service portal.

https://www.servicenow.com/community/developer-articles/getxmlwait-alternative-for-service-portal/ta...