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<!DOCTYPE html> 
<html> 
<head> 
<meta charset="utf-8"> 
<title>Wfuyu教程(wfuyu.com)</title> 
<script type="text/javascript">
function getValue(){
   var a,b,c;
   a = void ( b = 5, c = 7 );
   document.write('a = ' + a + ' b = ' + b +' c = ' + c );
}
</script>
</head>
<body>
    
<p>点击以下按钮查看结果：</p>
<form>
<input type="button" value="点我" onclick="getValue();" />
</form>
    
</body>
</html>