标签：-o desc 返回 ajax 不能 cut 使用 promise detail
地址：http://api.jquery.com/jQuery.when/
jQuery.when( deferreds )，returns Promise
正文
Description: Provides a way to execute callback functions based on zero or more Thenable objects, usually Deferred objects that represent asynchronous events.
描述：提供一个执行回调函数的方法，它是基于0或多个继发对象的，这些对象通常是表示异步事件的deferred对象。
deferreds
Type: Deferred or Promise or ThenableZero or more Thenable objects.
jQuery.when( deferreds )方法是 JQ1.5版本后添加的方法。传入的参数deferreds类型为deferred，promise，thenable，0或多个继发对象。
If no arguments are passed to
jQuery.when(), it will return a resolved Promise.
如果不传递参数给when，该方法将返回一个已完成状态的promise。关于Promise（参看：http://www.jianshu.com/p/063f7e490e9a）。
If a single Deferred is passed to
jQuery.when(), its Promise object (a subset of the Deferred methods) is returned by the method. Additional methods of the Promise object can be called to attach callbacks, such asdeferred.then. When the Deferred is resolved or rejected, usually by the code that created the Deferred originally, the appropriate callbacks will be called. For example, the jqXHR object returned byjQuery.ajax()is a Promise-compatible object and can be used this way:$.when( $.ajax( "test.aspx" ) ).then(function( data, textStatus, jqXHR ) {alert( jqXHR.status ); // Alerts 200});
If a single argument is passed to
jQuery.when()and it is not a Deferred or a Promise, it will be treated as a resolved Deferred and any doneCallbacks attached will be executed immediately. The doneCallbacks are passed the original argument. In this case any failCallbacks you might set are never called since the Deferred is never rejected. For example:$.when( { testing: 123 } ).done(function( x ) {alert( x.testing ); // Alerts "123"});
If you don‘t pass it any arguments at all, jQuery.when() will return a resolved promise.
$.when().then(function( x ) {
alert( "I fired immediately" );
});
如果不传递任何参数，jQuery.when()将返回一个完成状态的promise。In the case where multiple Deferred objects are passed tojQuery.when(), the method returns the Promise from a new "master" Deferred object that tracks the aggregate state of all the Deferreds it has been passed. The method will resolve its master Deferred as soon as all the Deferreds resolve, or reject the master Deferred as soon as one of the Deferreds is rejected. If the master Deferred is resolved, the doneCallbacks for the master Deferred are executed. The arguments passed to the doneCallbacks provide the resolved values for each of the Deferreds, and matches the order the Deferreds were passed tojQuery.when(). For example:var d1 = $.Deferred();var d2 = $.Deferred();$.when( d1, d2 ).done(function ( v1, v2 ) {console.log( v1 ); // "Fish"console.log( v2 ); // "Pizza"});d1.resolve( "Fish" );d2.resolve( "Pizza" );
var dtd = $.Deferred(); var wait=function(dtd){ setTimeout(task, 8000); function task(){ console.log("i‘m jiangtian!"); dtd.resolve(); } return dtd; } $.when(wait(dtd)).done(function(){ console.log("累死我了，终于执行完了。"); })
阮一峰这篇文章写的相当详细，推荐：《jQuery的deferred对象详解 - 阮一峰的网络日志》
In the event a Deferred was resolved with no value, the corresponding doneCallback argument will be undefined. If a Deferred resolved to a single value, the corresponding argument will hold that value. In the case where a Deferred resolved to multiple values, the corresponding argument will be an array of those values. For example:
var d1 = $.Deferred();var d2 = $.Deferred();var d3 = $.Deferred();$.when( d1, d2, d3 ).done(function ( v1, v2, v3 ) {console.log( v1 ); // v1 is undefinedconsole.log( v2 ); // v2 is "abc"console.log( v3 ); // v3 is an array [ 1, 2, 3, 4, 5 ]});d1.resolve();d2.resolve( "abc" );d3.resolve( 1, 2, 3, 4, 5 );
标签：-o desc 返回 ajax 不能 cut 使用 promise detail
原文地址：http://www.cnblogs.com/jiangtian/p/6906138.html
