一、input:file属性
属性值有以下几个比较常用：
accept：表示可以选择的文件MIME类型，多个MIME类型用英文逗号分开，常用的MIME类型见下表。
multiple：是否可以选择多个文件，多个文件时其value值为第一个文件的虚拟路径。
1、accept
只能选择png和gif图片
<input id="fileId1" type="file" accept="image/png,image/gif" name="file" />
2、multiple
多文件上传
<input id="fileId2" type="file" multiple="multiple" name="file" />
3、常用MIME类型
后缀名 MIME名称 *.3gpp audio/3gpp, video/3gpp *.ac3 audio/ac3 *.asf allpication/vnd.ms-asf *.au audio/basic *.css text/css *.csv text/csv *.doc application/msword *.dot application/msword *.dtd application/xml-dtd *.dwg image/vnd.dwg *.dxf image/vnd.dxf *.gif image/gif *.htm text/html *.html text/html *.jp2 image/jp2 *.jpe image/jpeg *.jpeg image/jpeg *.jpg image/jpeg *.js text/javascript, application/javascript *.json application/json *.mp2 audio/mpeg, video/mpeg *.mp3 audio/mpeg *.mp4 audio/mp4, video/mp4 *.mpeg video/mpeg *.mpg video/mpeg *.mpp application/vnd.ms-project *.ogg application/ogg, audio/ogg *.pdf application/pdf *.png image/png *.pot application/vnd.ms-powerpoint *.pps application/vnd.ms-powerpoint *.ppt application/vnd.ms-powerpoint *.rtf application/rtf, text/rtf *.svf image/vnd.svf *.tif image/tiff *.tiff image/tiff *.txt text/plain *.wdb application/vnd.ms-works *.wps application/vnd.ms-works *.xhtml application/xhtml+xml *.xlc application/vnd.ms-excel *.xlm application/vnd.ms-excel *.xls application/vnd.ms-excel *.xlt application/vnd.ms-excel *.xlw application/vnd.ms-excel *.xml text/xml, application/xml *.zip aplication/zip *.xlsx application/vnd.openxmlformats-officedocument.spreadsheetml.sheet