前言
el-upload的accept属性，可以接收限制上传文件的类型，官方文档的属性说明里，提示accpet就是input 类型type="file"控件的原生属性，那还是追踪溯源，来看看原生的input都怎么使用的？好吧，start~
关于<input type="file"/>
可以参考这个文档链接
// accept 接口一组逗号分隔的“唯一的文件类型说明符”，例如下方的例子
<input type="file" id="docpicker"
accept=".doc,.docx,application/msword,application/vnd.openxmlformats-officedocument.wordprocessingml.document">
关于“唯一的文件类型说明符”，官方也有例子补充，like this，总体来说，可以接收文件扩展名、MIME type、type/* （*代表所有这一类文件）
- A valid case-insensitive filename extension, starting with a period (".") character. For example:
.jpg,.pdf, or.doc. - A valid MIME type string, with no extensions.
- The string
audio/*meaning "any audio file". - The string
video/*meaning "any video file". - The string
image/*meaning "any image file".
关于MIME type
MIME type是媒体资源类型，以下是搜集的一些文件格式和type之间的映射
| 格式 | 值 | 其他补充 |
|---|---|---|
| *.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 |
| *.docx | application/vnd.openxmlformats-officedocument.wordprocessingml.document | 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-2000 |
| *.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-4 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 |
| 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 |
| *.xlsx | application/vnd.openxmlformats-officedocument.spreadsheetml.sheet | MS Excel Macro |
| *.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 |
