javascript - 發送請求時，時常在發起前多一條請求，會有哪些原因引起？

問題描述

接口都是CORS跨域

多出的一條請求：Request Method:OPTIONS、沒有傳遞參數

多出的條請求的response headers

Access-Control-Allow-Credentials:trueAccess-Control-Allow-Headers:Access-Control-Allow-Headers, Origin,Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-HeadersAccess-Control-Allow-Methods:POST, GET, PUT, OPTIONS, DELETEAccess-Control-Allow-Origin:*Access-Control-Max-Age:3600Allow:GET, HEAD, POST, PUT, DELETE, TRACE, OPTIONS, PATCHConnection:keep-aliveContent-Length:0Date:Fri, 05 May 2017 09:27:40 GMTServer:WildFly/10X-Powered-By:Undertow/1

正常請求的response headers

Access-Control-Allow-Credentials:trueAccess-Control-Allow-Headers:Access-Control-Allow-Headers, Origin,Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-HeadersAccess-Control-Allow-Methods:POST, GET, PUT, OPTIONS, DELETEAccess-Control-Allow-Origin:*Access-Control-Max-Age:3600Connection:keep-aliveContent-Type:application/json;charset=UTF-8Date:Fri, 05 May 2017 09:27:41 GMTServer:WildFly/10Set-Cookie:JSESSIONID=Zv7WiKxKZFNkE6ihLsGfGwYF8ZEFNEFxENl7rNLW.localhost; path=/bridgeTransfer-Encoding:chunkedX-Powered-By:Undertow/1

問題解答

跨域 post請求，需要option一次

樓上正解，如果是簡單的跨域請求，建議不要使用POST

你curl一下你的請求，應該就不會有這樣的預請求

1樓正解，跨域請求會先option一次到服務端，經過服務端驗證通過后，在發送請求