JavaScript 判断下传文件大小

<script type="text/javascript"> 
function getFileSize(filePath) { 
var image=new Image(); 
image.dynsrc=filePath; 
alert(image.fileSize); 
} 
</script> 
<body> 
<INPUT TYPE="file" NAME="file" SIZE="30" onchange="getFileSize(this.value)"> 
</body> 

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