我正在尝试以下代码:
var x=$.get();
x.promise();
var y=new $.Deferred();
y.promise();
至于在$.Deferred().promise and $.get().promise
之间进行比较.在这两种情况下(x.promise() 和 y.promise() ),Chrome 调试器都会将我带到同一行 jQuery 源代码:
promise: function( obj ) {
return obj != null ? jQuery.extend( obj, promise ) : promise;
}
但是,x.promise==y.promise
返回 false!!为什么?我无法给出解释...
我需要一些帮助。谢谢
ILIAS那是因为关于对象defer
和对象promise
的实例不同,即使它们从相同的代码创建......每次调用jQuery.Deferred
方法时都会创建新对象。
Deferred: function( func ) {
// notice, these define is in the Deferred method, every time is whole new object
var tuples = [
// action, add listener, listener list, final state
[ "resolve", "done", jQuery.Callbacks("once memory"), "resolved" ],
[ "reject", "fail", jQuery.Callbacks("once memory"), "rejected" ],
[ "notify", "progress", jQuery.Callbacks("memory") ]
],
state = "pending",
promise = {
state: function() {
return state;
},
always: function() {
deferred.done( arguments ).fail( arguments );
return this;
},
then: function( /* fnDone, fnFail, fnProgress */ ) {
var fns = arguments;
return jQuery.Deferred(function( newDefer ) {
jQuery.each( tuples, function( i, tuple ) {
var action = tuple[ 0 ],
fn = jQuery.isFunction( fns[ i ] ) && fns[ i ];
// deferred[ done | fail | progress ] for forwarding actions to newDefer
deferred[ tuple[1] ](function() {
var returned = fn && fn.apply( this, arguments );
if ( returned && jQuery.isFunction( returned.promise ) ) {
returned.promise()
.done( newDefer.resolve )
.fail( newDefer.reject )
.progress( newDefer.notify );
} else {
newDefer[ action + "With" ]( this === promise ? newDefer.promise() : this, fn ? [ returned ] : arguments );
}
});
});
fns = null;
}).promise();
},
// Get a promise for this deferred
// If obj is provided, the promise aspect is added to the object
promise: function( obj ) {
return obj != null ? jQuery.extend( obj, promise ) : promise;
}
},
deferred = {};