How to return false in javascript function from JQuery calling [web method] in asp.net

The AJAX call is asynchronous, so the function ends before the result arrives. The success function runs later, when the result arrives.

Change the AJAX request to be synchronous, to get the result before the function exists, by adding an async property to the ajax call:

async: false,

You could try a slightly different approach. When i do ajax calls using jquery i use the success and the error functions.

To make your ajax call end up in the error function you should make asp return a different http status code. I use status code 400 for this which means,

400 Bad Request

The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications.

Explanation status code can be found here

Here's and example i used today inside a colorbox:

$.ajax({
  type: 'POST',
  url: url,
  data: $(formSelector, '#cboxLoadedContent').serializeArray(),
  success: function() {
    $.colorbox.close();
    window.location.href = successurl;
  },
  error: function(jqXHR, textStatus, errorThrown){
    $('ul.errors', '#cboxLoadedContent').html(errorThrown);
    $.colorbox.resize();
  }
});

I'm not familiar with asp but this is how my php + symfony template error handling looks like (this sets the 400 and add errors which will be catched by my ajax call)

<?php
if ($sf_request->hasErrors()) {
  $errors = array();
  foreach ($sf_request->getErrors() as $error) {
    $errors[] = msI18N::translate($error);
  }

  sfContext::getInstance()->getResponse()->setStatusCode(400, '<li>' . implode('<li></li>', $errors) . '</li>');
}
?>

Hope this example give's you and idea how you could pull it off using asp.

Presumably, you want to return true where you have alert("its true"). Based on that premise, you will want to do one of two things:

Option 1. Use a synchronous ajax call. You would set a variable in your success function indicating the return value, and then return that value after the ajax call:

function test() {
    var areaId = 98;
    var returnVal;
    $.ajax({
        async: false,     //  Make it synchronous here
        type: "POST",
        url: "GridViewData.aspx/GetRegions",
        data: "{areaId:" + areaId + "}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function artybones(data) {
            returnVal = data.d == "Foo 98";  // set the return value
        }
    });
    return returnVal;   // return true or false
}

Then, check the result of test() to determine whether to call InsertUpdateData():

if (test())
{
    InsertUpdateData();
}

Option 2. Call InsertUpdateData() from the success callback. You can either pass it to test() as a parameter or hard code it in test(). Here's the hard coded technique:

function test() {
    var areaId = 98;
    var returnVal;
    $.ajax({
        type: "POST",
        url: "GridViewData.aspx/GetRegions",
        data: "{areaId:" + areaId + "}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function artybones(data) {
            if(data.d == "Foo 98")
            {
                InsertUpdateData();
            }
        }
    });
}

Here's passing it as a parameter:

function test(fnDataMatch) {
    var areaId = 98;
    var returnVal;
    $.ajax({
        type: "POST",
        url: "GridViewData.aspx/GetRegions",
        data: "{areaId:" + areaId + "}",
        contentType: "application/json; charset=utf-8",
        dataType: "json",
        success: function artybones(data) {
            if(data.d == "Foo 98")
            {
                fnDataMatch();
            }
        }
    });
}

Then, call test() like so:

test(InsertUpdateData);