Executing a synchronous request using $ .ajax

Question

we know that only synchronous requests are executed with $ .ajax with the async option: false But I saw in the jQuery manual that "synchronous requests can temporarily block the browser by disabling any actions while the request is active." I have some questions, such as

I saw several answers saying to use callback () How can I get jQuery to execute a synchronous rather than asynchronous Ajax request? . How can I implement this for my function.

In the function below, if the request fails or the response is not returned. How can I process it. I can use "error:" or something like this. How can I improve this feature effectively, I mean using callback and error handling. They say that (we can never get a mistake and success with a request)

function empvalidate() {
          var exists = false;             // default return value is false
          var empno = $("#empno").val();
          if (empno != '') {
            $.ajax({
              url: "emp.php",
              async: false,
              dataType: "json",
              data: {'param1': $("#param1").val(), 'empno': $("#empno").val()},
              success: function (data) {
                exists = data.status;     // set status of existence to outer variable
              }
            });
          }
          return exists;                  // return actual value
        }

Answer 1

Your synchronized request will cause the user interface thread (and therefore the browser) to wait until the object XMLHttpRequestreturns (the view regardless of whether it was unsuccessful or successfully completed).

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Answer 2

async: false - :

function begin_ajax() {
    // Set your UI states here
}

function success_ajax(data) {
    // Run whatever needs to run if the request is successful.
}

function error_ajax(xhr, error_type, msg) {
    // Display error messages
}

function complete_ajax() {
    // Clean up UI
}
$.ajax({
    beforeSend: begin_ajax,
    success: success_ajax,
    error: error_ajax,
    complete: complete_ajax
    // Your parameters here
});

Answer 3

""

jQuery Docs

(XMLHttpRequest, textStatus) -

, ( ). : XMLHttpRequest , ( "", "notmodified", "error", "timeout" "Parsererror" ). Ajax.

ajax:

function empvalidate() {
      var exists = false;             // default return value is false
      var empno = $("#empno").val();
      if (empno != '') {
        $.ajax({
          url: "emp.php",
          async: false,
          dataType: "json",
          data: {'param1': $("#param1").val(), 'empno': $("#empno").val()},
          success: function (data, ts) {

              if(ts == "success")
                   exists = data.status; // set status of existence to outer variable
              else if(ts == "timeout")
              {
                   $(document).trigger('customTimeoutHandler');
              }
          }
        });
      }
      return exists;                  // return actual value
    }

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