How to return response from function which may use ajax call?

Question

In my java script there is one function which return status(Available, Not Available, etc).

var status;
var cookieItem=getFromCookie('abc');
switch(cookieItem){
    case '0':
       status='Available';
       break;
    case '1':
       status='Not Available';
       break;
    default:
       status=_getFromServer();
       break;
}
return status;


function() _getFromServer(){
    $.ajax({
       type: 'GET',
       url: apiUrl,
       contentType: 'application/json',
       success: function (response) {
           return 'Available';
       },
       error: function (xhr) {
           return 'Not Available';
       }
    });

}

Here, _getFromServer() is async. So if user gets status from cookie is's fine but if there is no cookie available then it will return 'undefined' as _getFromServer is async.

I don't know how can I achieve my requirements.

I search on internet net and I found this question of SO, but I don't know how can it fulfill my requirements.