_http_outgoing.js:504
throw new Error('Can\'t set headers after they are sent.');
^
Error: Can't set headers after they are sent.
at validateHeader (_http_outgoing.js:504:11)
at ServerResponse.setHeader (_http_outgoing.js:511:3)
at Array.write (D:\GitSpace\fbms\node_modules\_finalhandler@1.0.3@finalhandl
er\index.js:254:9)
at listener (D:\GitSpace\fbms\node_modules\_on-finished@2.3.0@on-finished\in
dex.js:169:15)
at onFinish (D:\GitSpace\fbms\node_modules\_on-finished@2.3.0@on-finished\in
dex.js:100:5)
at callback (D:\GitSpace\fbms\node_modules\_ee-first@1.1.1@ee-first\index.js
:55:10)
at IncomingMessage.onevent (D:\GitSpace\fbms\node_modules\_ee-first@1.1.1@ee
-first\index.js:93:5)
at emitNone (events.js:105:13)
at IncomingMessage.emit (events.js:207:7)
at endReadableNT (_stream_readable.js:1045:12)
at _combinedTickCallback (internal/process/next_tick.js:102:11)
at process._tickCallback (internal/process/next_tick.js:161:9)
Program node app.js exited with code 1
Wenn Sie den Debugging-Modus nicht starten, tritt beim Laden der Seite kein Fehler auf, req und res sind alle normal
代码写的有问题，跟调试模式无关，response响应已经被发送了，但是你却仍然想修改已经被发送的响应头。
一旦调用 response.end() 方法，代表此响应已经结束并发送，在此之后不得调用诸如 response.writeHead() 等修改 response 的方法。