jquery.ajax.js

/* Commonly Misused jQuery AJAX Settings: */

// As of jQuery 2.x
$.ajax({
  accept: 'json', // Tells the server the format the client accepts back
  dataType: 'json', // When set to 'json', will pre-parse the JSON for you
  error: function () {
    console.log("Oh no we got a 500!"); // Callback for server errors and timeouts/bad responses
  },
  success: function () {
    console.log("We got a 200!"); // Callback for if the function succeeds/response is ok
  },
  complete: function () {
    console.log("Totally done"); // Callback for when request is done, executes after .success and .error, always executes
  }
});

// As of jQuery 3.x - .success, .fail, .complete have been deprecated
$.ajax({
  fail: function () {
    console.log("Oh no we got a 500!"); // Same as .error
  },
  done: function () {
    console.log("We got a 200!"); // Same as .success
  },
  always: function () {
    console.log("Totally done"); // Same as .complete
  }
});

// To check jQuery version:
console.log(jQuery().jquery);