当客户端想要下载文件时,nodejs服务端如何根据URL设置响应头的Content-Type类型
".cpp": "text/plain", ".cpt": "application/mac-compactpro", ".crd": "application/x-mscardfile", ".crl": "application/pkix-crl", ".crt": "application/x-x509-ca-cert", ".csh": "application/x-csh", ".csm": "chemical/x-csml", ".csml": "chemical/x-csml", ".css": "text/css",