accept限制上传文件类型
<input type="file" accept="" />
accept的值为：
| 格式 | accept类型 |
|---|---|
| *.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 |
| 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 |
| .xltx | application/vnd.openxmlformats-officedocument.spreadsheetml.template |
| .potx | application/vnd.openxmlformats-officedocument.presentationml.template |
| .ppsx | application/vnd.openxmlformats-officedocument.presentationml.slideshow |
| .pptx | application/vnd.openxmlformats-officedocument.presentationml.presentation |
| .sldx | application/vnd.openxmlformats-officedocument.presentationml.slide |
| .docx | application/vnd.openxmlformats-officedocument.wordprocessingml.document |
| .dotx | application/vnd.openxmlformats-officedocument.wordprocessingml.template |
| .xlsm | application/vnd.ms-excel.addin.macroEnabled.12 |
| .xlsb | application/vnd.ms-excel.sheet.binary.macroEnabled.12 |
