docs: 翻译错误修正

aio/content/guide/comparing-observables.md

@@ -270,7 +270,7 @@ The following code snippets illustrate how the same kind of operation is defined
 
 Observables are very similar to event handlers that use the events API. Both techniques define notification handlers, and use them to process multiple values delivered over time. Subscribing to an observable is equivalent to adding an event listener. One significant difference is that you can configure an observable to transform an event before passing the event to the handler.
 
-可观察对象和事件 API 中的事件处理器很像。这两种技术都会定义通知处理器，并使用它们来处理一段时间内传递的多个值。订阅可观察对象与添加事件处理器是等价的。一个显著的不同是你可以配置可观察对象，使其在把事件传给事件处理器之间先进行转换。
+可观察对象和事件 API 中的事件处理器很像。这两种技术都会定义通知处理器，并使用它们来处理一段时间内传递的多个值。订阅可观察对象与添加事件处理器是等价的。一个显著的不同是你可以配置可观察对象，使其在把事件传给事件处理器之前先进行转换。
 
 Using observables to handle events and asynchronous operations can have the advantage of greater consistency in contexts such as HTTP requests.