Research on the Input Button Function of Type File

<br />When uploading on some websites, a [Select File] dialog box will pop up after clicking the "Browse" button. Many times we need to upload only image files, then in the pop-up [Select File] dialog box only files of related image formats are displayed, and all other formats of files are filtered out and not displayed.
For example, http://www.youku.com/v1.0.0326/v/swf/up.swf
This is Youku's video upload option, which uses the FLASH method to prevent non-video files from being displayed.
FLASH to this effect is generally as described here
import flash.net.FileReferenceList;
var fileRef:FileReferenceList = new FileReferenceList();
var allTypes:Array = [];
var browse type:Object = new Object();
Browsing type.description = "Browsing type (*.mp3)";
Browse type.extension = "*.mp3";
allTypes.push(browse type);
fileRef.browse(allTypes);
So for the <input type="File"> in our web page, can we also implement a pop-up window to limit the file type?
The current solution is to remind users that the format of the uploaded file is incorrect through monitoring.
<script>
function check(){
var filepath=path.value
filepath=filepath.substring(filepath.lastIndexOf('.') 1,filepath.length)
if(filepath != 'jpg' && filepath != 'gif')
alert("Only JPG or GIF format images can be uploaded")
}
</script>
<input type=file name=path onpropertychange="check()"> (Only JPG or GIF format images can be uploaded)
<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>
<form>
<input type=file name=path onpropertychange="ck(this)"/></form>
However, this effect is obviously not as good as the user experience of FLASH. It is necessary to pay attention to this type of FLASH upload.

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