Why i can not fetch data from controller from ajax function?

Question

I'm beginner in asp.net mvc ,and want to fetch simple json from controller to ajax variable,for that purpose in view page write this ajax function:

<script>
    var OutPut;
    OutPut = "behzad";
    function CallService() {
        $.ajax({
            url: '@Url.Action("callService", "myPassword")',
            type: 'GET',
            dataType: 'json',
            cache: false,
            data: { 'id': 2 },
            success: function (color) {
                OutPut= color;

            },
            error: function () {
                alert('Error occured');
            }
        });
        alert("I think is ok!"+":"+OutPut);

    }
</script>

and this controller:

[HttpGet]
        public JsonResult callService(int id)
        {
            string JSON = "behzad";
            return Json(JSON,JsonRequestBehavior.AllowGet);

        }

that ajax function call with this html code in view page:

<button type="button" class="btn btn-success" onclick="CallService()">Success</button>

but this line in ajax function:

alert("I think is ok!"+":"+OutPut);

Output is undefined,what happen?is controller return null?or why i get undefined alert?thanks.

ajax is async and your alert(..) will be called before your ajax call returns a value. In the code you have shown, the output will be "behzad" (not undefined) because you have declared it globally. — user3559349
– user3559349, Commented May 8, 2016 at 5:58

Darin Dimitrov · Accepted Answer · 2016-05-08 06:04:04Z

2

Since the AJAX call is asynchronous, you should place the alert inside the success callback:

<script>
    function CallService() {
        $.ajax({
            url: '@Url.Action("callService", "myPassword")',
            type: 'GET',
            cache: false,
            data: { 'id': 2 },
            success: function (color) {
                alert("I think is ok!" + ":" + color);
            },
            error: function () {
                alert('Error occurred');
            }
        });
    }
</script>

answered May 8, 2016 at 6:04

Darin Dimitrov

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