why the javascript variable doesn't change among function?

Question

my problem with the following javascript function:

function ValidateDates() {

var valid = false;
birthD = $("#cp1_txtBirthDate").val();
initialD = $("#cp1_txtInitialDate").val();
var regexp = new RegExp("^([1-9]|(0|1|2)[0-9]|30)(/)([1-9]|1[0-2]|0[1-9])(/)((20|19|18)[0-9]{2})$");

if (birthD != "__/__/____" && initialD != "__/__/____") {
    if (regexp.test(initialD) && regexp.test(birthD)) {

        $.get("ValidateDates.aspx?BirthD=" + birthD + "&InitialD=" + initialD, function (data) {
            if (data == 0) {
                valid = true;

                $("#Dates_span").html("");
            }

            else {
                $("#Dates_span").html("*" + data);
                valid = false;

            }

        });

    }
}

return valid;
}

here when i check the variable valid i found it "false" even if its true, because the initial for it is false from the beginning of function so how to solve it and what is wrong?

You have not described clearly what is wrong. – gideon Mar 26 '12 at 08:56 — gideon, Mar 26 '12 at 08:56

score 6 · Accepted Answer · answered Mar 26 '12 at 08:57

6

When you're doing an asynchronous call, you can't return a value like that. Instead, you should pass in a callback:

function ValidateDates(callback) {

    var valid = false;
    birthD = $("#cp1_txtBirthDate").val();
    initialD = $("#cp1_txtInitialDate").val();
    var regexp = new RegExp("^([1-9]|(0|1|2)[0-9]|30)(/)([1-9]|1[0-2]|0[1-9])(/)((20|19|18)[0-9]{2})$");

    if (birthD != "__/__/____" && initialD != "__/__/____") {
        if (regexp.test(initialD) && regexp.test(birthD)) {

            $.get("ValidateDates.aspx?BirthD=" + birthD + "&InitialD=" + initialD, function(data) {
                if (data == 0) {
                    valid = true;

                    $("#Dates_span").html("");
                }

                else {
                    $("#Dates_span").html("*" + data);
                    valid = false;

                }
                callback(valid);
            });
        }
    }
}

Then, call it like:

ValidateDates(function(isValid)
{
   // Do something with isValid
});

answered Mar 26 '12 at 08:57

Matthew Flaschen

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sorry but i am stuck with something, i want the returned value to use it in if condition with other function like this :if (Page_ClientValidate() && ValidateName() && ValidNull && ValidateDates) so how to deal with this? – special life Mar 26 '12 at 09:51
If ValidateDates is the only async one, you can just put the others inside the function. Otherwise, you can chain the async calls using multiple functions. – Matthew Flaschen Mar 26 '12 at 13:20
how to make chain because i have many ajax calls for validation and i am using validatePage function that contains all validation to check before submit the page as "client side function" and "has returned value true or false – special life Mar 27 '12 at 05:23
@speciallife, you could make a server-side wrapper function to do all the validation in one AJAX call. Alternatively, see [this answer](http://stackoverflow.com/questions/995529/how-to-chain-ajax-requests). – Matthew Flaschen Mar 27 '12 at 13:05

score 1 · Answer 2 · answered Mar 26 '12 at 08:57

What's wrong is that $.get is an asynchronous call, what that means is that the function doesn't wait until the result is returned from $.get call. It just makes the call and continues execution - so valid = true is set long after false has been returned.

why the javascript variable doesn't change among function?

2 Answers2