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。
<input id="fileId1" type="file" accept="image/png,image/gif" name="file" />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