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
": "video/3gpp", ".aab": "application/x-authoware-bin", ".aam": "application/x-authoware-map", ".aas": "application/x-authoware-seg", ".acx": "application/internet-property-stream", ".ai": "application/postscript", ".aif": "audio/x-aiff", ".aifc": "audio/x-aiff", ".aiff": "a