请教：javascript如何捕获方向键？

用window.event.keyCode不行？
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 1<body onkeydown="alert(event.keyCode)">   
 2  
 3← 37   
 4↑ 38   
 5→ 39   
 6↓ 40   
 7\---------------------------------------------------------------   
 8  
 9在哪里都一样   
10<html>
11<head>
12<title>键盘和鼠标事件测试</title>
13<script language="javascript">   
14<!--   
15function viewEvent(e) {   
16s = "";   
17s = event.srcElement.tagName+"<br>";   
18for(v in event)   
19s += v+"="+event[v]+"<br>";   
20view.innerHTML = s;   
21}   
22  
23document.onkeydown=viewEvent   
24document.onkeyup=viewEvent   
25document.onmousedown=viewEvent   
26document.onmouseup=viewEvent   
27document.onmousemove=viewEvent   
28document.onmouseover=viewEvent   
29document.onmouseout=viewEvent   
30document.onkeypress=viewEvent   
31  
32//-->   
33</script>
34</head>
35<body>
36<form>
37<input type="text"/>
38<textarea></textarea>
39</form>
40<table border="">
41<tr><td>123</td><td>123</td></tr>
42</table>
43<span id="view"></span>
44</body>
45</html></body>