'checkExpectation' 事件

• request <http.IncomingMessage>
• response <http.ServerResponse>

每次收到带有 HTTP Expect 标头的请求时触发，其中值不是 100-continue。 如果未监听此事件，则服务器将根据需要自动响应 417 Expectation Failed。

处理和处理此事件时，不会触发 'request' 事件。

• request <http.IncomingMessage>
• response <http.ServerResponse>

Emitted each time a request with an HTTP Expect header is received, where the value is not 100-continue. If this event is not listened for, the server will automatically respond with a 417 Expectation Failed as appropriate.

When this event is emitted and handled, the 'request' event will not be emitted.