Research on the Input button function of JavaScript type File_Form special effects

For example, http://www.youku.com/v1.0.0326/v/swf/up.swf
This is Youku’s video upload option, which uses FLASH to prevent non-video files from being displayed.
FLASH to this effect is generally as described here

Copy code The code is as follows:

import flash.net.FileReferenceList;
var fileRef:FileReferenceList = new FileReferenceList();
var allTypes:Array = [];
var browse type:Object = new Object();
Browse type.description = "Browse type(*.mp3)";
Browse type.extension = "*.mp3";
allTypes.push(browse type);
fileRef.browse(allTypes );

So for the in our webpage, can we also implement pop-up windows to limit file types?
The current solution can only be to remind users that the format of the uploaded file is incorrect through monitoring

<input type="file" name="path" onpropertychange="check()"> (Only images in JPG or GIF format can be uploaded)
[Ctrl A Select all Note: If you need to introduce external Js, you need to refresh to execute

]

<form> <input type="file" name="path" onpropertychange="ck(this)"> </form>
[Ctrl A Select all Note:

If you need to introduce external Js, you need to refresh to execute
]
<script> function check(){ var filepath=path.value filepath=filepath.substring(filepath.lastIndexOf('.')+1,filepath.length) if(filepath != 'jpg' && filepath != 'gif') alert("只能上传JPG或GIF格式的图片") } </script>However, this effect obviously does not FLASH has a good user experience. It is necessary to pay attention to this type of FLASH upload. <script> function ck(obj){if(obj.value.length>0){ var af="jpg,gif,png,zip,rar,txt,htm"; if(eval("with(obj.value)if(!/"+af.split(",").join("|")+"/ig.test(substring(lastIndexOf('.')+1,length)))1;")){alert("Allowed file types:\n"+af);obj.createTextRange().execCommand('delete')}; }} </script>