用于包装异步JavaScript函数以使其同步的模式 [英] Pattern for wrapping an Asynchronous JavaScript function to make it synchronous

问题描述

我正在使用JavaScript API，其中大部分功能是异步的。 API是 WebKit JavaScript数据库API 这是绑定到操作SQLite3数据库的功能子集。我了解设计决定使事情异常，以阻止和提供响应式用户界面。在我的情况下，我知道我使用异步API调用将执行得很快。因为这样，我想为开发人员提供一个更干净，更易于使用的包装API，强制同步调用。

这是异步调用

  db.executeSql（sqlStatement，function（result）{
 // do something with result 
}）; 
  

这是我想要做的

  var result = dbWrapper.executeSql（sqlStatement）; 
 //做一些结果
  

有没有设计模式/方法来做到这一点？写入或链接到代码示例是首选。目标平台/手机是iPhone上的Mobile Safari。

谢谢

解决方案

对不起，JavaScript不提供语言原语（例如线程或协同程序），以使异步事件同步进行，反之亦然。

你一般*得到一个执行线程，所以您无法从定时器或XMLHttpRequest readystatechange获取回调，直到导致创建请求的堆栈完全解开。

*：除了某些模糊的情况不会帮助你，而且通常被认为是错误

I'm working with a JavaScript API where most of the functions are asynchronous. The API is the WebKit JavaScript Database API which is a binding to a subset of functionality to manipulate SQLite3 databases. I understand the design decision to make things async as to not block and provide a responsive user interface. In my situation I know that my usage of the async API calls will execute fast. Since this is the case I'd like to provide my developers a cleaner and easier to use wrapper API that forces synchronous calls.

Here's the async call

db.executeSql(sqlStatement, function(result) {
  // do something with result
});

And here's what I'd like to be able to do

var result = dbWrapper.executeSql(sqlStatement);
// do something with result

Is there a design pattern/way to do this? A written or linked to code example is preferred. The target platform/broswer is Mobile Safari on the iPhone.

Thank you

解决方案

Sorry, JavaScript does not provide the language primitives (eg. threads or coroutines) to make asynchronous things act synchronously or vice-versa.

You generally* get one thread of execution only, so you can't get a callback from a timer or XMLHttpRequest readystatechange until the stack of calls leading to the creation of the request has completely unravelled.

So in short, you can't really do it; the approach with nested closures on the WebKit page you linked is the only way I know of to make the code readable in this situation.

*: except in some obscure situations which wouldn't help you and are generally considered bugs

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