在做项目项目中经常需要上传文件，类型也就那几种。虽然在js中加了上传文件类型的限制，但是为了减少因为用户选择不当而造成的反复检验。可以在input标签上加上accept属性。这种限制只是优化了选择文件的过程，但是没法真正做到限制文件类型因为：
看到没有，是可以选择的。所以还得以自己的验证代码为准。
浏览器支持情况
Internet Explorer 10、Firefox、Opera、Chrome 和 Safari 6 支持 accept 属性。
注意：Internet Explorer 9 及之前的版本都不支持 <input> 标签的 accept 属性。
用法
可以单个限制使用也可以组合使用 比如：
<input accept="audio/*,video/*,image/*" />
<input accept="audio/*" />
<input accept="image/png" />
另外附上一些文件对应类型
*.3gpp audio/3gpp， video/3gpp 3GPP Audio/Video
*.ac3 audio/ac3 AC3 Audio
*.asf allpication/vnd.ms-asf Advanced Streaming Format
*.au audio/basic AU Audio
*.css text/css Cascading Style Sheets
*.csv text/csv Comma Separated Values
*.doc application/msword MS Word Document
*.dot application/msword MS Word Template
*.dtd application/xml-dtd Document Type Definition
*.dwg image/vnd.dwg AutoCAD Drawing Database
*.dxf image/vnd.dxf AutoCAD Drawing Interchange Format
*.gif image/gif Graphic Interchange Format
*.htm text/html HyperText Markup Language
*.html text/html HyperText Markup Language
*.jp2 image/jp2 JPEG-
*.jpe image/jpeg JPEG
*.jpeg image/jpeg JPEG
*.jpg image/jpeg JPEG
*.js text/javascript， application/javascript JavaScript
*.json application/json JavaScript Object Notation
*.mp2 audio/mpeg， video/mpeg MPEG Audio/Video Stream， Layer II
*.mp3 audio/mpeg MPEG Audio Stream， Layer III
*.mp4 audio/mp4， video/mp4 MPEG- Audio/Video
*.mpeg video/mpeg MPEG Video Stream， Layer II
*.mpg video/mpeg MPEG Video Stream， Layer II
*.mpp application/vnd.ms-project MS Project Project
*.ogg application/ogg， audio/ogg Ogg Vorbis
*.pdf application/pdf Portable Document Format
*.png image/png Portable Network Graphics
*.pot application/vnd.ms-powerpoint MS PowerPoint Template
*.pps application/vnd.ms-powerpoint MS PowerPoint Slideshow
*.ppt application/vnd.ms-powerpoint MS PowerPoint Presentation
*.rtf application/rtf， text/rtf Rich Text Format
*.svf image/vnd.svf Simple Vector Format
*.tif image/tiff Tagged Image Format File
*.tiff image/tiff Tagged Image Format File
*.txt text/plain Plain Text
*.wdb application/vnd.ms-works MS Works Database
*.wps application/vnd.ms-works Works Text Document
*.xhtml application/xhtml+xml Extensible HyperText Markup Language
*.xlc application/vnd.ms-excel MS Excel Chart
*.xlm application/vnd.ms-excel MS Excel Macro
*.xls application/vnd.ms-excel MS Excel Spreadsheet
*.xlt application/vnd.ms-excel MS Excel Template
*.xlw application/vnd.ms-excel MS Excel Workspace
*.xml text/xml， application/xml Extensible Markup Language
*.zip aplication/zip Compressed Archive