jQuery jQuery.Deferred () method
Definition and Usage
$ .Deferred () Constructor is a function that returns a practical object method to register chain multiple callbacks, and calls the callback queue, any synchronous or asynchronous transfer function succeeded or failed state.
Tip: 1. $ .Deferred () constructor creates a new Deferred (delay) objects, jQuery.Deferred can pass an optional function, the function is called and passed a new Deferred object before the constructor returns as a function the first argument. For example, the called function can use deferred.then () to attach a callback function.
2. a Deferred object starts in a suspended state. Any use deferred.then (), deferred.always (), deferred.done (), or deferred.fail () callback function added to the object are queued for execution. Call deferred.resolve () or eferred.resolveWith () conversion delay to resolve the status immediately after execution doneCallbacks set. Executive failCallbacks set immediately call deferred.reject () or deferred.rejectWith () after conversion delay to reject state. Once an object has entered the state resolved or rejected, it remains in this state. You can still add a callback to have been resolved or rejected Deferred objects - they will be executed immediately.
grammar
| 参数 | 描述 |
|---|---|
| beforeStart | Function( Deferred deferred )类型 一个在构造函数返回之前调用的函数 |