十八、Node.js创建Web服务器（二）

在上一篇文章中我们在自定义模块自定义了几种文件类型的头文件加工的方法：

/**
 * 自定义模块加工响应头文件类型
 */
module.exports.getminiName=function (extname) {
    switch (extname){
        case ".html":
            return "text/html"
        case ".css":
            return"text/css"
        case ".js":
            return "text/js"
        case ".xml":
            return"text/xml"
        default:
            return"text/xml"
    }
}

但是我们知道，一个html文件除了自己会去加载所引入的上面这几种文件，可能还需要加载img，video，zip等等，很多骑她类型的文件，因此上面这种加工就是辅助我们理解头文件的加工原理的，现实开发中是满足不了的；

下面我整理了一个后缀名对应头文件的json文件，基本上包含了所有的文件类型，下面我们看看如何从该json文件里面解析获取头文件：

项目结构截图：

mime.json代碼：

{ ".323":"text/h323" ,
  ".3gp":"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":"audio/x-aiff" ,
  ".als":"audio/X-Alpha5" ,
  ".amc":"application/x-mpeg" ,
  ".ani":"application/octet-stream" ,
  ".apk":"application/vnd.android.package-archive" ,
  ".asc":"text/plain" ,
  ".asd":"application/astound" ,
  ".asf":"video/x-ms-asf" ,
  ".asn":"application/astound" ,
  ".asp":"application/x-asap" ,
  ".asr":"video/x-ms-asf" ,
  ".asx":"video/x-ms-asf" ,
  ".au":"audio/basic" ,
  ".avb":"application/octet-stream" ,
  ".avi":"video/x-msvideo" ,
  ".awb":"audio/amr-wb" ,
  ".axs":"application/olescript" ,
  ".bas":"text/plain" ,
  ".bcpio":"application/x-bcpio" ,
  ".bin ":"application/octet-stream" ,
  ".bld":"application/bld" ,
  ".bld2":"application/bld2" ,
  ".bmp":"image/bmp" ,
  ".bpk":"application/octet-stream" ,
  ".bz2":"application/x-bzip2" ,
  ".c":"text/plain" ,
  ".cal":"image/x-cals" ,
  ".cat":"application/vnd.ms-pkiseccat" ,
  ".ccn":"application/x-cnc" ,
  ".cco":"application/x-cocoa" ,
  ".cdf":"application/x-cdf" ,
  ".cer":"application/x-x509-ca-cert" ,
  ".cgi":"magnus-internal/cgi" ,
  ".chat":"application/x-chat" ,
  ".class":"application/octet-stream" ,
  ".clp":"application/x-msclip" ,
  ".cmx":"image/x-cmx" ,
  ".co":"application/x-cult3d-object" ,
  ".cod":"image/cis-cod" ,
  ".conf":"text/plain" ,
  ".cpio":"application/x-cpio" ,
  ".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" ,
  ".cur":"application/octet-stream" ,
  ".dcm":"x-lml/x-evm" ,
  ".dcr":"application/x-director" ,
  ".dcx":"image/x-dcx" ,
  ".der":"application/x-x509-ca-cert" ,
  ".dhtml":"text/html" ,
  ".dir":"application/x-director" ,
  ".dll":"application/x-msdownload" ,
  ".dmg":"application/octet-stream" ,
  ".dms":"application/octet-stream" ,
  ".doc":"application/msword" ,
  ".docx":"application/vnd.openxmlformats-officedocument.wordprocessingml.document" ,
  ".dot":"application/msword" ,
  ".dvi":"application/x-dvi" ,
  ".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" ,
  ".epub":"application/epub+zip" ,
  ".eri":"image/x-eri" ,
  ".es":"audio/echospeech" ,
  ".esl":"audio/echospeech" ,
  ".etc":"application/x-earthtime" ,
  ".etx":"text/x-setext" ,
  ".evm":"x-lml/x-evm" ,
  ".evy":"application/envoy" ,
  ".exe":"application/octet-stream" ,
  ".fh4":"image/x-freehand" ,
  ".fh5":"image/x-freehand" ,
  ".fhc":"image/x-freehand" ,
  ".fif":"application/fractals" ,
  ".flr":"x-world/x-vrml" ,
  ".flv":"flv-application/octet-stream" ,
  ".fm":"application/x-maker" ,
  ".fpx":"image/x-fpx" ,
  ".fvi":"video/isivideo" ,
  ".gau":"chemical/x-gaussian-input" ,
  ".gca":"application/x-gca-compressed" ,
  ".gdb":"x-lml/x-gdb" ,
  ".gif":"image/gif" ,
  ".gps":"application/x-gps" ,
  ".gtar":"application/x-gtar" ,
  ".gz":"application/x-gzip" ,
  ".h":"text/plain" ,
  ".hdf":"application/x-hdf" ,
  ".hdm":"text/x-hdml" ,
  ".hdml":"text/x-hdml" ,
  ".hlp":"application/winhlp" ,
  ".hqx":"application/mac-binhex40" ,
  ".hta":"application/hta" ,
  ".htc":"text/x-component" ,
  ".htm":"text/html" ,
  ".html":"text/html" ,
  ".hts":"text/html" ,
  ".htt":"text/webviewhtml" ,
  ".ice":"x-conference/x-cooltalk" ,
  ".ico":"image/x-icon" ,
  ".ief":"image/ief" ,
  ".ifm":"image/gif" ,
  ".ifs":"image/ifs" ,
  ".iii":"application/x-iphone" ,
  ".imy":"audio/melody" ,
  ".ins":"application/x-internet-signup" ,
  ".ips":"application/x-ipscript" ,
  ".ipx":"application/x-ipix" ,
  ".isp":"application/x-internet-signup" ,
  ".it":"audio/x-mod" ,
  ".itz":"audio/x-mod" ,
  ".ivr":"i-world/i-vrml" ,
  ".j2k":"image/j2k" ,
  ".jad":"text/vnd.sun.j2me.app-descriptor" ,
  ".jam":"application/x-jam" ,
  ".jar":"application/java-archive" ,
  ".java":"text/plain" ,
  ".jfif":"image/pipeg" ,
  ".jnlp":"application/x-java-jnlp-file" ,
  ".jpe":"image/jpeg" ,
  ".jpeg":"image/jpeg" ,
  ".jpg":"image/jpeg" ,
  ".jpz":"image/jpeg" ,
  ".js":"application/x-javascript" ,
  ".jwc":"application/jwc" ,
  ".kjx":"application/x-kjx" ,
  ".lak":"x-lml/x-lak" ,
  ".latex":"application/x-latex" ,
  ".lcc":"application/fastman" ,
  ".lcl":"application/x-digitalloca" ,
  ".lcr":"application/x-digitalloca" ,
  ".lgh":"application/lgh" ,
  ".lha":"application/octet-stream" ,
  ".lml":"x-lml/x-lml" ,
  ".lmlpack":"x-lml/x-lmlpack" ,
  ".log":"text/plain" ,
  ".lsf":"video/x-la-asf" ,
  ".lsx":"video/x-la-asf" ,
  ".lzh":"application/octet-stream" ,
  ".m13":"application/x-msmediaview" ,
  ".m14":"application/x-msmediaview" ,
  ".m15":"audio/x-mod" ,
  ".m3u":"audio/x-mpegurl" ,
  ".m3url":"audio/x-mpegurl" ,
  ".m4a":"audio/mp4a-latm" ,
  ".m4b":"audio/mp4a-latm" ,
  ".m4p":"audio/mp4a-latm" ,
  ".m4u":"video/vnd.mpegurl" ,
  ".m4v":"video/x-m4v" ,
  ".ma1":"audio/ma1" ,
  ".ma2":"audio/ma2" ,
  ".ma3":"audio/ma3" ,
  ".ma5":"audio/ma5" ,
  ".man":"application/x-troff-man" ,
  ".map":"magnus-internal/imagemap" ,
  ".mbd":"application/mbedlet" ,
  ".mct":"application/x-mascot" ,
  ".mdb":"application/x-msaccess" ,
  ".mdz":"audio/x-mod" ,
  ".me":"application/x-troff-me" ,
  ".mel":"text/x-vmel" ,
  ".mht":"message/rfc822" ,
  ".mhtml":"message/rfc822" ,
  ".mi":"application/x-mif" ,
  ".mid":"audio/mid" ,
  ".midi":"audio/midi" ,
  ".mif":"application/x-mif" ,
  ".mil":"image/x-cals" ,
  ".mio":"audio/x-mio" ,
  ".mmf":"application/x-skt-lbs" ,
  ".mng":"video/x-mng" ,
  ".mny":"application/x-msmoney" ,
  ".moc":"application/x-mocha" ,
  ".mocha":"application/x-mocha" ,
  ".mod":"audio/x-mod" ,
  ".mof":"application/x-yumekara" ,
  ".mol":"chemical/x-mdl-molfile" ,
  ".mop":"chemical/x-mopac-input" ,
  ".mov":"video/quicktime" ,
  ".movie":"video/x-sgi-movie" ,
  ".mp2":"video/mpeg" ,
  ".mp3":"audio/mpeg" ,
  ".mp4":"video/mp4" ,
  ".mpa":"video/mpeg" ,
  ".mpc":"application/vnd.mpohun.certificate" ,
  ".mpe":"video/mpeg" ,
  ".mpeg":"video/mpeg" ,
  ".mpg":"video/mpeg" ,
  ".mpg4":"video/mp4" ,
  ".mpga":"audio/mpeg" ,
  ".mpn":"application/vnd.mophun.application" ,
  ".mpp":"application/vnd.ms-project" ,
  ".mps":"application/x-mapserver" ,
  ".mpv2":"video/mpeg" ,
  ".mrl":"text/x-mrml" ,
  ".mrm":"application/x-mrm" ,
  ".ms":"application/x-troff-ms" ,
  ".msg":"application/vnd.ms-outlook" ,
  ".mts":"application/metastream" ,
  ".mtx":"application/metastream" ,
  ".mtz":"application/metastream" ,
  ".mvb":"application/x-msmediaview" ,
  ".mzv":"application/metastream" ,
  ".nar":"application/zip" ,
  ".nbmp":"image/nbmp" ,
  ".nc":"application/x-netcdf" ,
  ".ndb":"x-lml/x-ndb" ,
  ".ndwn":"application/ndwn" ,
  ".nif":"application/x-nif" ,
  ".nmz":"application/x-scream" ,
  ".nokia-op-logo":"image/vnd.nok-oplogo-color" ,
  ".npx":"application/x-netfpx" ,
  ".nsnd":"audio/nsnd" ,
  ".nva":"application/x-neva1" ,
  ".nws":"message/rfc822" ,
  ".oda":"application/oda" ,
  ".ogg":"audio/ogg" ,
  ".oom":"application/x-AtlasMate-Plugin" ,
  ".p10":"application/pkcs10" ,
  ".p12":"application/x-pkcs12" ,
  ".p7b":"application/x-pkcs7-certificates" ,
  ".p7c":"application/x-pkcs7-mime" ,
  ".p7m":"application/x-pkcs7-mime" ,
  ".p7r":"application/x-pkcs7-certreqresp" ,
  ".p7s":"application/x-pkcs7-signature" ,
  ".pac":"audio/x-pac" ,
  ".pae":"audio/x-epac" ,
  ".pan":"application/x-pan" ,
  ".pbm":"image/x-portable-bitmap" ,
  ".pcx":"image/x-pcx" ,
  ".pda":"image/x-pda" ,
  ".pdb":"chemical/x-pdb" ,
  ".pdf":"application/pdf" ,
  ".pfr":"application/font-tdpfr" ,
  ".pfx":"application/x-pkcs12" ,
  ".pgm":"image/x-portable-graymap" ,
  ".pict":"image/x-pict" ,
  ".pko":"application/ynd.ms-pkipko" ,
  ".pm":"application/x-perl" ,
  ".pma":"application/x-perfmon" ,
  ".pmc":"application/x-perfmon" ,
  ".pmd":"application/x-pmd" ,
  ".pml":"application/x-perfmon" ,
  ".pmr":"application/x-perfmon" ,
  ".pmw":"application/x-perfmon" ,
  ".png":"image/png" ,
  ".pnm":"image/x-portable-anymap" ,
  ".pnz":"image/png" ,
  ".pot,":"application/vnd.ms-powerpoint" ,
  ".ppm":"image/x-portable-pixmap" ,
  ".pps":"application/vnd.ms-powerpoint" ,
  ".ppt":"application/vnd.ms-powerpoint" ,
  ".pptx":"application/vnd.openxmlformats-officedocument.presentationml.presentation" ,
  ".pqf":"application/x-cprplayer" ,
  ".pqi":"application/cprplayer" ,
  ".prc":"application/x-prc" ,
  ".prf":"application/pics-rules" ,
  ".prop":"text/plain" ,
  ".proxy":"application/x-ns-proxy-autoconfig" ,
  ".ps":"application/postscript" ,
  ".ptlk":"application/listenup" ,
  ".pub":"application/x-mspublisher" ,
  ".pvx":"video/x-pv-pvx" ,
  ".qcp":"audio/vnd.qcelp" ,
  ".qt":"video/quicktime" ,
  ".qti":"image/x-quicktime" ,
  ".qtif":"image/x-quicktime" ,
  ".r3t":"text/vnd.rn-realtext3d" ,
  ".ra":"audio/x-pn-realaudio" ,
  ".ram":"audio/x-pn-realaudio" ,
  ".rar":"application/octet-stream" ,
  ".ras":"image/x-cmu-raster" ,
  ".rc":"text/plain" ,
  ".rdf":"application/rdf+xml" ,
  ".rf":"image/vnd.rn-realflash" ,
  ".rgb":"image/x-rgb" ,
  ".rlf":"application/x-richlink" ,
  ".rm":"audio/x-pn-realaudio" ,
  ".rmf":"audio/x-rmf" ,
  ".rmi":"audio/mid" ,
  ".rmm":"audio/x-pn-realaudio" ,
  ".rmvb":"audio/x-pn-realaudio" ,
  ".rnx":"application/vnd.rn-realplayer" ,
  ".roff":"application/x-troff" ,
  ".rp":"image/vnd.rn-realpix" ,
  ".rpm":"audio/x-pn-realaudio-plugin" ,
  ".rt":"text/vnd.rn-realtext" ,
  ".rte":"x-lml/x-gps" ,
  ".rtf":"application/rtf" ,
  ".rtg":"application/metastream" ,
  ".rtx":"text/richtext" ,
  ".rv":"video/vnd.rn-realvideo" ,
  ".rwc":"application/x-rogerwilco" ,
  ".s3m":"audio/x-mod" ,
  ".s3z":"audio/x-mod" ,
  ".sca":"application/x-supercard" ,
  ".scd":"application/x-msschedule" ,
  ".sct":"text/scriptlet" ,
  ".sdf":"application/e-score" ,
  ".sea":"application/x-stuffit" ,
  ".setpay":"application/set-payment-initiation" ,
  ".setreg":"application/set-registration-initiation" ,
  ".sgm":"text/x-sgml" ,
  ".sgml":"text/x-sgml" ,
  ".sh":"application/x-sh" ,
  ".shar":"application/x-shar" ,
  ".shtml":"magnus-internal/parsed-html" ,
  ".shw":"application/presentations" ,
  ".si6":"image/si6" ,
  ".si7":"image/vnd.stiwap.sis" ,
  ".si9":"image/vnd.lgtwap.sis" ,
  ".sis":"application/vnd.symbian.install" ,
  ".sit":"application/x-stuffit" ,
  ".skd":"application/x-Koan" ,
  ".skm":"application/x-Koan" ,
  ".skp":"application/x-Koan" ,
  ".skt":"application/x-Koan" ,
  ".slc":"application/x-salsa" ,
  ".smd":"audio/x-smd" ,
  ".smi":"application/smil" ,
  ".smil":"application/smil" ,
  ".smp":"application/studiom" ,
  ".smz":"audio/x-smd" ,
  ".snd":"audio/basic" ,
  ".spc":"application/x-pkcs7-certificates" ,
  ".spl":"application/futuresplash" ,
  ".spr":"application/x-sprite" ,
  ".sprite":"application/x-sprite" ,
  ".sdp":"application/sdp" ,
  ".spt":"application/x-spt" ,
  ".src":"application/x-wais-source" ,
  ".sst":"application/vnd.ms-pkicertstore" ,
  ".stk":"application/hyperstudio" ,
  ".stl":"application/vnd.ms-pkistl" ,
  ".stm":"text/html" ,
  ".svg":"image/svg+xml" ,
  ".sv4cpio":"application/x-sv4cpio" ,
  ".sv4crc":"application/x-sv4crc" ,
  ".svf":"image/vnd" ,
  ".svg":"image/svg+xml" ,
  ".svh":"image/svh" ,
  ".svr":"x-world/x-svr" ,
  ".swf":"application/x-shockwave-flash" ,
  ".swfl":"application/x-shockwave-flash" ,
  ".t":"application/x-troff" ,
  ".tad":"application/octet-stream" ,
  ".talk":"text/x-speech" ,
  ".tar":"application/x-tar" ,
  ".taz":"application/x-tar" ,
  ".tbp":"application/x-timbuktu" ,
  ".tbt":"application/x-timbuktu" ,
  ".tcl":"application/x-tcl" ,
  ".tex":"application/x-tex" ,
  ".texi":"application/x-texinfo" ,
  ".texinfo":"application/x-texinfo" ,
  ".tgz":"application/x-compressed" ,
  ".thm":"application/vnd.eri.thm" ,
  ".tif":"image/tiff" ,
  ".tiff":"image/tiff" ,
  ".tki":"application/x-tkined" ,
  ".tkined":"application/x-tkined" ,
  ".toc":"application/toc" ,
  ".toy":"image/toy" ,
  ".tr":"application/x-troff" ,
  ".trk":"x-lml/x-gps" ,
  ".trm":"application/x-msterminal" ,
  ".tsi":"audio/tsplayer" ,
  ".tsp":"application/dsptype" ,
  ".tsv":"text/tab-separated-values" ,
  ".ttf":"application/octet-stream" ,
  ".ttz":"application/t-time" ,
  ".txt":"text/plain" ,
  ".uls":"text/iuls" ,
  ".ult":"audio/x-mod" ,
  ".ustar":"application/x-ustar" ,
  ".uu":"application/x-uuencode" ,
  ".uue":"application/x-uuencode" ,
  ".vcd":"application/x-cdlink" ,
  ".vcf":"text/x-vcard" ,
  ".vdo":"video/vdo" ,
  ".vib":"audio/vib" ,
  ".viv":"video/vivo" ,
  ".vivo":"video/vivo" ,
  ".vmd":"application/vocaltec-media-desc" ,
  ".vmf":"application/vocaltec-media-file" ,
  ".vmi":"application/x-dreamcast-vms-info" ,
  ".vms":"application/x-dreamcast-vms" ,
  ".vox":"audio/voxware" ,
  ".vqe":"audio/x-twinvq-plugin" ,
  ".vqf":"audio/x-twinvq" ,
  ".vql":"audio/x-twinvq" ,
  ".vre":"x-world/x-vream" ,
  ".vrml":"x-world/x-vrml" ,
  ".vrt":"x-world/x-vrt" ,
  ".vrw":"x-world/x-vream" ,
  ".vts":"workbook/formulaone" ,
  ".wav":"audio/x-wav" ,
  ".wax":"audio/x-ms-wax" ,
  ".wbmp":"image/vnd.wap.wbmp" ,
  ".wcm":"application/vnd.ms-works" ,
  ".wdb":"application/vnd.ms-works" ,
  ".web":"application/vnd.xara" ,
  ".wi":"image/wavelet" ,
  ".wis":"application/x-InstallShield" ,
  ".wks":"application/vnd.ms-works" ,
  ".wm":"video/x-ms-wm" ,
  ".wma":"audio/x-ms-wma" ,
  ".wmd":"application/x-ms-wmd" ,
  ".wmf":"application/x-msmetafile" ,
  ".wml":"text/vnd.wap.wml" ,
  ".wmlc":"application/vnd.wap.wmlc" ,
  ".wmls":"text/vnd.wap.wmlscript" ,
  ".wmlsc":"application/vnd.wap.wmlscriptc" ,
  ".wmlscript":"text/vnd.wap.wmlscript" ,
  ".wmv":"audio/x-ms-wmv" ,
  ".wmx":"video/x-ms-wmx" ,
  ".wmz":"application/x-ms-wmz" ,
  ".wpng":"image/x-up-wpng" ,
  ".wps":"application/vnd.ms-works" ,
  ".wpt":"x-lml/x-gps" ,
  ".wri":"application/x-mswrite" ,
  ".wrl":"x-world/x-vrml" ,
  ".wrz":"x-world/x-vrml" ,
  ".ws":"text/vnd.wap.wmlscript" ,
  ".wsc":"application/vnd.wap.wmlscriptc" ,
  ".wv":"video/wavelet" ,
  ".wvx":"video/x-ms-wvx" ,
  ".wxl":"application/x-wxl" ,
  ".x-gzip":"application/x-gzip" ,
  ".xaf":"x-world/x-vrml" ,
  ".xar":"application/vnd.xara" ,
  ".xbm":"image/x-xbitmap" ,
  ".xdm":"application/x-xdma" ,
  ".xdma":"application/x-xdma" ,
  ".xdw":"application/vnd.fujixerox.docuworks" ,
  ".xht":"application/xhtml+xml" ,
  ".xhtm":"application/xhtml+xml" ,
  ".xhtml":"application/xhtml+xml" ,
  ".xla":"application/vnd.ms-excel" ,
  ".xlc":"application/vnd.ms-excel" ,
  ".xll":"application/x-excel" ,
  ".xlm":"application/vnd.ms-excel" ,
  ".xls":"application/vnd.ms-excel" ,
  ".xlsx":"application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" ,
  ".xlt":"application/vnd.ms-excel" ,
  ".xlw":"application/vnd.ms-excel" ,
  ".xm":"audio/x-mod" ,
  ".xml":"text/plain",
  ".xml":"application/xml",
  ".xmz":"audio/x-mod" ,
  ".xof":"x-world/x-vrml" ,
  ".xpi":"application/x-xpinstall" ,
  ".xpm":"image/x-xpixmap" ,
  ".xsit":"text/xml" ,
  ".xsl":"text/xml" ,
  ".xul":"text/xul" ,
  ".xwd":"image/x-xwindowdump" ,
  ".xyz":"chemical/x-pdb" ,
  ".yz1":"application/x-yz1" ,
  ".z":"application/x-compress" ,
  ".zac":"application/x-zaurus-zac" ,
  ".zip":"application/zip" ,
  ".json":"application/json"
}

自定义模块，用来加工并返回头文件的getmimeFromFile.js文件代码：

下面是错误代码：

var  fs=require("fs")
module.exports={
    getMime:function (etxName) {
        fs.readFile("./mime.json",function (err,data) {
            if (err){
                console.log('mime.json文件不存在');
            }else {
                //console.log(data.toString());//将十六进制转换为字符串
                var  mimes=JSON.parse(data.toString());//将json字符串转换为json对象
                //console.log(mimes[etxName]);
                return (mimes[etxName]||"text/html")+"111111111111111111111"//返回对应的头文件形式，如果没有的话就返回text/html
                /**
                 * 注意  fs.readFile()方法是异步的，非阻塞的，getMime方法在被调用的时候fs.readFile()的回调函数并没执行，也就是说
                 * getMime()方法根本没有返回值
                 * 解决方法1：使用同步方法：fs.readFileSync()
                 */
            }
        })
    }
}

解决方法1：使用同步方法：fs.readFileSync()

module.exports={
    getMime:function (extname) {
        var data=fs.readFileSync("./mime.json");//这里使用同步方法，注意同步方法读取文件直接返回读取内容
        var mime=JSON.parse(data.toString())[extname];
        return mime||"text/html";
    }
}

解决方法2：使用回调函数解决异步问题：

 var fs=require("fs")
 function getdata(callback) {
     fs.readFile("./mime.json", function (err, data) {
         callback(data)
     })
 }
 getdata(function (result) {
     console.log(result.toString());
     /**
      * 在调用getdata方法时，如果getdata方法里面有异步方法，但是我们又必须使用异步方法的返回数据
      * ，那么我们就可以在getdata方法里面的回调函数里面获取到异步方法里面的数据来使用
      */
 })