是否可以直接通过AJAX创建和使用Deferred对象？

Question

I have an application which sends a few AJAX requests when a user clicks a specific button.

However, I also have something similar to a 'Cancel' button, which should abort all requests.

I'm using $.when currently to handle all of the requests sent, with appropriate callbacks added onto the Promise object it returns.

However, the fact that $.when returns a Promise object is frustrating, as it doesn't (deliberately) include the methods Deferred has to control the requests, as shown with this code:

Using $.when

var x = $.when($.get('/'), $.get('/')); // .then(function() {console.log('done');});

Object.keys(x); 
// ["state", "always", "then", "promise", "pipe", "done", "fail", "progress"]

Using one AJAX request (jqXHR implements the Deferred interface)

var x = $.get('/');

Object.keys(x); 
// ["readyState", "getResponseHeader", "getAllResponseHeaders", "setRequestHeader", "overrideMimeType", "statusCode", "abort", "state", "always", "then", "promise", "pipe", "done", "fail", "progress", "complete", "success", "error"]

I'm looking for a way to retrieve the Deferred object, or replace $.when with a method which performs the same, but returns a Deferred object instead. From there, I will be able to call a suitable reject / abort method.

Is this possible?

Answer 1

You can put the requests into an array and abort them individually when you need to.

For this you can use .apply on $.when . For example:

var requests = [$.get('/'), $.get('/')];
$.when.apply($,requests).then(function(res1,res2){
      //access results here
});

// aborting:
requests.forEach(function(x){ return x.abort();});

Deferred objects are only used to create promises from callback APIs. You can not 'retrieve' the deferred object of an already existing promise. Only create new ones using it.

You might also want to look into Domenic's last() .