JavaScript控制打开文件另存为对话框_JavaScript

通过JS打开图片另存为对话框，提示用户保存文件
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> 
<html> 
<head> 
<title> New Document </title> 
<meta name="Generator" content="EditPlus"> 
<meta name="Author" content=""> 
<meta name="Keywords" content=""> 
<meta name="Description" content=""> 
<script src="http://ajax.useso.com/ajax/libs/jquery/1.3.2/jquery.min.js" type="text/javascript"></script> 
<script language="JavaScript"> 
<!-- 
function downLoadImage(imagePathURL){ 
//如果中间IFRAME不存在，则添加 
if(!document.getElementById("_SAVEASIMAGE_TEMP_FRAME")) 
jQuery('<iframe style="display:none;" id="_SAVEASIMAGE_TEMP_FRAME" name="_SAVEASIMAGE_TEMP_FRAME" onload="_doSaveAsImage();" 
width="0" height="0" src="about:blank"></iframe>').appendTo("body"); 
if(document.all._SAVEASIMAGE_TEMP_FRAME.src!=imagePathURL){ 
//图片地址发生变化，加载图片 
document.all._SAVEASIMAGE_TEMP_FRAME.src = imagePathURL; 
}else{ 
//图片地址没有变化，直接另存为 
_doSaveAsImage(); 
} 
} 
function _doSaveAsImage(){ 
if(document.all._SAVEASIMAGE_TEMP_FRAME.src!="about:blank") 
document.frames("_SAVEASIMAGE_TEMP_FRAME").document.execCommand("SaveAs"); 
} 
//--> 
</script> 
</head> 
<body> 
<input type="button" value="download image" onclick="downLoadImage('http://www.blogjava.net/images/blogjava_net/weiwei/46570/r_beyond1991.jpg');"> 
</body> 
</html>