关于HTML5 IndexedDB的异步API疑惑 [英] Doubts about HTML5 IndexedDB Async API

问题描述

在阅读 HTML5索引规格我有关于它的异步请求模式有些怀疑。当在看请求API例如，在打开方法用于启动异步请求。

  VAR请求= indexedDB.open（地址簿，地址簿）;
request.onsuccess =功能（EVT）{...};
request.onerror =功能（EVT）{...};
 

目前请求开始时的时间，不存在的事件处理程序尚未定义

• 这不是一个竞争条件？


• 在打开方法成功会发生什么的JavaScript间preTER之前执行分配到的onSuccess ？


• 或者是才真正开始请求一次回调都被注册？

在我看来像下面的API会更合乎逻辑的：

  db.open（地址簿，地址簿，{
    的onSuccess：功能（E）{...}，
    的onerror：功能（E）{...}
}）;
 

解决方案

有将没有竞争条件，因为JavaScript引擎将完成执行实际范围（功能），然后引发任何回调或事件处理程序。阅读下面的<一个href=\"http://hacks.mozilla.org/2010/06/comparing-indexeddb-and-webdatabase/comment-page-1/#comment-92830\">comment在Mozilla黑客。

While reading the HTML5 IndexedDB Specification I had some doubts about its asynchronous request model. When looking at the request api example, the open method is used to start an async request.

var request = indexedDB.open('AddressBook', 'Address Book');
request.onsuccess = function(evt) {...};
request.onerror = function(evt) {...};

At the time this request is started, there are no event handlers defined yet.

• Isn't this a race condition?
• What happens when the open method succeeds before the javascript interpreter executes the assignment to onsuccess?
• Or is the request only really started once both callbacks are registered?

In my opinion an api like the following would be much more logical:

db.open('AddressBook', 'Address Book', {
    onsuccess: function(e) { ... },
    onerror  : function(e) { ... }
});

解决方案

There will be no race condition because JavaScript engine will finish executing actual scope (function) and then fire any callback or event handler. Read following comment on Mozilla Hacks.

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