Question

I have this jquery call to ajax,

function findTaxForProcess(argPrc, argPrcAmount, argPrcDiscount) {
            if (argPrc == '') { return 0; };
            var _valToReturn;

            if ($('#hdnTaxBefore').val() == "true") {
                // if tax is calculated before discount
                $.ajax({
                    url: '/AutoComplete.asmx/FindProcessTax',
                    type: 'POST',
                    timeout: 5000,
                    datatype: 'xml',
                    cache: false,
                    data: 'argProcess=' + argPrc + '&argAmt=' + argPrcAmount,
                    success: function (response) {
                        _valToReturn = $(response).find('double').text();
                        alert(_valToReturn);
                    }
                });
            }

            else {
                // the tax is calculated after discount
                $.ajax({
                    url: '/AutoComplete.asmx/FindProcessTaxAter',
                    type: 'POST',
                    timeout: 5000,
                    datatype: 'xml',
                    cache: false,
                    data: 'argProcess=' + argPrc + '&argAmt=' + argPrcAmount + '&argDiscount=' + argPrcDiscount,
                    success: function (response) {
                        _valToReturn = $(response).find('double').text();
                        alert(_valToReturn);
                    }
                });
            }
            alert('came here ' + _valToReturn);
            return _valToReturn;
        };

The problem is first alert shows 2.873 (in the else case, it shows 2.178), but the problem is second alert, the second alert shows , came here undefined??? FTW? what the hack is going wrong? I’ve been messing around this for 2 days but nothing!

Why is the value of _valToReturn undefined at second alert? and defined at first? any help?

EDIT : The alert came here _valToReturn is executing after the first alert. So, as (almost!) all answerer said that if its coming before, it would be undefined, I know that, but as I said it is executing after not before.

Answer 1

Ajax is an asynchronous request. By the time the success event executes, the alert “came here undefined” would have executed. And the variable has not been initialized by then.

Update:
In answer to your question looking closely, I believe
The anonymous function sees valToReturn as a local variable. Hence those variables are on a different “stack” if you will.

See this:
Javascript anonymous function not updating global variable

Or

Using variable outside of ajax callback function

Similar to yours.