层的移动-键盘按钮触发事件

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<img src="images/fish.gif" width="128" height="128">
<font color="#FF99FF" font-size="15">
<h4>这本来是一条鱼的.555...."<br/>"分别用A-S-D-W控制我的游动方向......<h4>
</font></div>

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function moveFish()
{
var fish=document.getElementById("divFish"); 
var nKey=event.keyCode;
//alert(nKey);
if(nKey==65 || nKey==37)
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fish.style.pixelLeft -=20; 
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if(nKey==87 || nKey==38)
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fish.style.pixelTop -=20;
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if(nKey==68 || nKey==39)
{
fish.style.pixelLeft +=20;
}
if(nKey==83 || nKey==40)
{
fish.style.pixelTop +=20;
}
}document.onkeydown=moveFish;
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