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                        /JavaScript入門篇

請問一下，第15行那個open()函數(shù)只能用window調(diào)用嗎？不能用上面定義的pr變量調(diào)用嗎

<!DOCTYPE?html>
<html>
?<head>
??<title>?new?document?</title>??
??<meta?http-equiv="Content-Type"?content="text/html;?charset=gbk"/>???
??<script?type="text/javascript">??
????function?openWindow()
????{
???????var?co=confirm("新窗口是否打開?")
???????if(co==true)
???????{
???????????var?pr=prompt("確定打開網(wǎng)址","http://www.baidu.com/");
???????????if(pr!=null)
???????????{
??????????????window.open(pr,"_blank",'width=400','height=500','menubar=no','toolbar=no');
???????????}
???????????else
???????????{
???????????????alert("再見");
???????????}
???????}
??????else
??????{
??????????alert("再見");
??????}
????}
????//?新窗口打開時彈出確認框，是否打開
????//?通過輸入對話框，確定打開的網(wǎng)址，默認為?http：//idcbgp.cn/
????//打開的窗口要求，寬400像素，高500像素，無菜單欄、無工具欄。
????
????
??</script>?
?</head>?
?<body>?
???<input?type="button"?value="新窗口打開網(wǎng)站"?onclick="openWindow()"?/>?
?</body>
</html>