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
.dwf": "drawing/x-dwf", ".dwg": "application/x-autocad", ".dxf": "application/x-autocad", ".dxr": "application/x-director", ".ebk": "application/x-expandedbook", ".emb": "chemical/x-embl-dl-nucleotide", ".embl": "chemical/x-embl-dl-nucleotide", ".eps": "application/postscript",