jquery - Use success() or complete() in AJAX call

Question

I want to understand the AJAX call below, in terms of the complete() method;

When I replace complete() with success(), I get an empty responseText just as with the AJAX error() method.

On the other hand, when I leave the complete() method there as it is, everything works as expected.

Is it that success() returns earlier than complete()?

$("#formnaw").submit(function() {
  var fnc = invoerFnc.attr("value");
  var vnaam = invoerVnaam.attr("value");
  var anaam = invoerAnaam.attr("value");
  var str1 = invoerStr1.attr("value");
  var nr1 = invoerNr1.attr("value");
  var pc1 = invoerPc1.attr("value");
  var pl1 = invoerPl1.attr("value");
  var tel1 = invoerTel1.attr("value");
  var mob1 = invoerMob1.attr("value");
  var em1 = invoerEm1.attr("value");
  var goknop = $("#formnaw > .instelling_go");
  //we deactiveren de submit knop tijdens het verzenden 
  goknop.attr({
    disabled: true
  });
  goknop.blur();
  //stuur de post variabelen naar livetabs.php
  $.ajax({
    type: "POST",
    url: "registraties/instellingenact.php",
    data: "actie=wijzignaw&vnaam=" + vnaam + "&anaam=" + anaam + "&functie=" + fnc + "&straat=" + str1 + "&nr=" + nr1 + "&postcode=" + pc1 + "&plaats=" + pl1 + "&tel=" + tel1 + "&mob=" + mob1 + "&email=" + em1,
    timeout: 5000,
    success: function(data, textStatus) {
        alert('bij success');
        //doe iets
      } //EINDE success
      ,
    error: function(XMLHttpRequest, textStatus, errorThrown) {
        if (textStatus == 'timeout') {
          //doe iets
        } else if (textStatus == 'error') {
          //doe iets
        }
        //her-activeer de zend knop
        goknop.attr({
          disabled: false
        });
      } //EINDE error
      ,
    complete: function(data) {
        updatelijst.append(data.responseText + "<br>");
        if (data.responseText.indexOf("Fout") != -1) {
          $('#formnaw').find('td.foutnr1').prepend(data.responseText);
        } else {
          updatelijst.animate({
            opacity: 'show'
          }, 1000, function() {});
        }
        //her-activeer de zend knop
        goknop.attr({
          disabled: false
        });
      } //EINDE complete
  }); //EINDE ajax
  //we stoppen het standaard gedrag van een submit, zodat de pagina niet wordt vernieuwd.
  return false;
});

Answer 1

Is it that success() returns earlier than complete()?

Yes; the AJAX success() method runs before the complete() method.

Below is a diagram illustrating the process flow:

It is important to note that

• The success() (Local Event) is only called if the request was successful (no errors from the server, no errors with the data).

• On the other hand, the complete() (Local Event) is called regardless of if the request was successful, or not. You will always receive a complete callback, even for synchronous requests.

... more details on AJAX Events here.