jQuery Deferred 的完成与成功回调

Question

Are there any technical differences between the following callback methods?

1

$.ajax({
  ...
  success: function(data, textStatus, jqXHR) {
    foo(data);
  },
  error: function (jqXHR, textStatus, errorThrown ) {
    bar();
  }
});

2

$.ajax(...)
  .done(function(data) {
    foo(data);
  })
  .fail(function() {
    bar();
  });

3

$.ajax(...)
  .then(function(data) {
    foo(data);
  }, function() {
    bar();
  });

With little experience, I am not sure they are correct examples for passing data to foo() . (Please correct me if I am wrong.)

With done / fail , we can't track other data like jqXHR , textStatus , errorThrown , etc. Am I right?

Is there a complete equivalence for the done / fail method?

From your experience, is one better than/preferred over the others at certain situations?

If I use both success and done / then , will one run before the other definitely or it can't be certain which will run before the other definitely? Or is using success and done / then altogether not recommended?

Answer 1

One difference between jQuery .done() and .then() is the return value can be changed at .then()

See jQuery deferreds and promises - .then() vs .done()

 $.Deferred(function(dfd) { dfd.resolve(1) }) .done(function(n) { return n + 1 }) .then(function(res) { console.log(res) // 1 })

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"> </script>

 $.Deferred(function(dfd) { dfd.resolve(1) }) .then(function(n) { return n + 1 }) .then(function(res) { console.log(res) // 2 })

 <script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"> </script>