What does 'rejected' mean for Deffered objects other than jqXHRs?

Question

From deferred.fail() page :

Description: Add handlers to be called when the Deferred object is rejected.

and the exmple:

$.get("test.php")
.done(function(){ alert("$.get succeeded"); })
.fail(function(){ alert("$.get failed!"); });

As we know, we can create var someObject = $.Deferred();

My questions:

• How can we 'Reject' a Deferred if it's not a jqXHR?

• How to implement deferred.fail() for Deferred objects other than jqXHR?

Thanks.

Yes, I know my English is bad.

Answer 1

A deferred object is rejected when either .reject() or .rejectWith() is called on it.

Here's an example:

var deferred = $.Deferred();
deferred
  .done(function() { console.log('done') })
  .fail(function() { console.log('failed') });

deferred.resolve(); // <-- will write 'done' to console
deferred.reject();  // <-- will write 'failed' to console

You can use deferreds to make asynchronous functions behave like $.get() does. For example setTimeout:

function MyTimeout() {
  var deferred = $.Deferred();

  setTimeout(function() {
    // as a demo, this will reject the deferred half the time
    if (Math.random() < 0.5)
      deferred.reject();
    else
      deferred.resolve();
  }, 2000);
  return deferred.promise();
}

MyTimeout()
  .done(function() { console.log('done') })
  .fail(function() { console.log('failed') });

The last statement can also be written as:

MyTimeout().then(
  function() { console.log('done') },
  function() { console.log('failed') }
);