为什么不将CORS标头添加到OPTIONS路由允许浏览器访问我的API？

问题：

I am trying to support CORS in my Node.js application that uses the Express.js web framework. 我正在尝试在使用Express.js Web框架的Node.js应用程序中支持CORS。 I have read a Google group discussion about how to handle this, and read a few articles about how CORS works. 我已经阅读了有关如何处理此问题的Google小组讨论，并阅读了一些有关CORS工作原理的文章。 First, I did this (code is written in CoffeeScript syntax): 首先，我做到了（代码是用CoffeeScript语法编写的）：

app.options "*", (req, res) ->
  res.header 'Access-Control-Allow-Origin', '*'
  res.header 'Access-Control-Allow-Credentials', true
  # try: 'POST, GET, PUT, DELETE, OPTIONS'
  res.header 'Access-Control-Allow-Methods', 'GET, OPTIONS'
  # try: 'X-Requested-With, X-HTTP-Method-Override, Content-Type, Accept'
  res.header 'Access-Control-Allow-Headers', 'Content-Type'
  # ...

It doesn't seem to work. 它似乎不起作用。 It seems like my browser (Chrome) is not sending the initial OPTIONS request. 看来我的浏览器（Chrome）没有发送初始的OPTIONS请求。 When I just updated the block for the resource I need to submit a cross-origin GET request to: 当我刚刚更新资源块时，我需要向以下站点提交跨域GET请求：

app.get "/somethingelse", (req, res) ->
  # ...
  res.header 'Access-Control-Allow-Origin', '*'
  res.header 'Access-Control-Allow-Credentials', true
  res.header 'Access-Control-Allow-Methods', 'POST, GET, PUT, DELETE, OPTIONS'
  res.header 'Access-Control-Allow-Headers', 'Content-Type'
  # ...

It works (in Chrome). 它可以工作（在Chrome中）。 This also works in Safari. 这也适用于Safari。

I have read that... 我读过...

In a browser implementing CORS, each cross-origin GET or POST request is preceded by an OPTIONS request that checks whether the GET or POST is OK. 在实现CORS的浏览器中，每个跨域的GET或POST请求之前都有一个OPTIONS请求，该请求检查GET或POST是否正常。

So my main question is, how come this doesn't seem to happen in my case? 所以我的主要问题是，在我看来，这种情况怎么似乎没有发生？ Why isn't my app.options block called? 为什么不调用我的app.options块？ Why do I need to set the headers in my main app.get block? 为什么需要在主app.get块中设置标题？