(仿百度,google输入框提示功能)提示功能的向下按键, 向上按键

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 <input type="text" id="query" onkeyup="beKeyUp(event)"/><br>   
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<div id="search_suggest" style="display:none;position:absolute;z-index:1;width:358px;border:1px solid #BCD7E8;margin:0;background:#fff;top:285px;left:6px;">   
<div style="font-size:15px;font-family:Arial,sans-serif;" id="TipsContent1">白菜</div>
<div style="font-size:15px;font-family:Arial,sans-serif;" id="TipsContent2">什么是白菜</div>
<div style="font-size:15px;font-family:Arial,sans-serif;" id="TipsContent3">白菜百科</div>
<div style="font-size:15px;font-family:Arial,sans-serif;" id="TipsContent4">白菜吃法</div>
</div>
<script>   
var checkNo = 0;   
var _search_suggest;   
function beKeyUp(oEvent){
	var oEvent=oEvent||window.event;
	var numCharCode=oEvent.keyCode||oEvent.which;
	if(numCharCode==32||numCharCode==49||numCharCode==50||numCharCode==51||numCharCode==52||numCharCode==53){		
		var key = document.getElementById("query").value;
		if(key.length<=1){
			return;
		}
		alert("这里是跟后台打交道,在这里为了演示输入框提示功能,默认提示信息有四条。支持IE6\7，FF3.0.x\3.5.x");
		document.getElementById('search_suggest').style.display="block";
		//ajax.ajax(key);
	}else if(numCharCode==40){
		if(checkNo==4){
			checkNo = 0;
		}
		checkNo = checkNo + 1;	
		/******恢复上一次按键的默认颜色(向下键每次都恢复上一层<div>的默认颜色值,如果huifuse等于0,说明上一次按下得键是第一次按或者上一次按下得键是最后一层<div>)******/
		var huifuse = checkNo-1;//恢复色的拼音,恢复上一次的颜色值为默认颜色值
		if(huifuse==0){//表示已经选择第一个,那么上一次按下键的值应该是最后一个值
			huifuse = 4;//恢复默认颜色的层
		}
		document.getElementById('TipsContent'+huifuse).style.color = "#000";   
       	document.getElementById('TipsContent'+huifuse).style.backgroundColor = "#fff";   
       	document.getElementById('TipsContent'+huifuse).focus();  
        /******恢复上一次按键的默认颜色(向下键每次都恢复上一层<div>的默认颜色值,如果huifuse等于0,说明上一次按下得键是第一次按或者上一次按下得键是最后一层<div>)******/
		document.getElementById('TipsContent'+checkNo).style.color = "white";   
        document.getElementById('TipsContent'+checkNo).style.backgroundColor = "blue";   
        document.getElementById('TipsContent'+checkNo).focus();  
	}else if(numCharCode==38){
		if(checkNo==1){
			checkNo = 4+1;
		}
		checkNo = checkNo - 1;
		/******恢复上一次按键的默认颜色(向上键每次都恢复下一层<div>的默认颜色值,如果huifuse等于5,说明上一次按下得键是第一层)******/
		var huifuse = checkNo+1;//恢复色的拼音,恢复上一次的颜色值为默认颜色值
		if(huifuse==5){//表示已经选择第一个,那么上一次按下键的值应该是最后一个值
			huifuse = 1;//恢复默认颜色的层
		}
		document.getElementById('TipsContent'+huifuse).style.color = "#000";   
       	document.getElementById('TipsContent'+huifuse).style.backgroundColor = "#fff";   
       	document.getElementById('TipsContent'+huifuse).focus(); 
       	/******恢复上一次按键的默认颜色******/
		document.getElementById('TipsContent'+checkNo).style.color = "white";   
        document.getElementById('TipsContent'+checkNo).style.backgroundColor = "blue";   
        document.getElementById('TipsContent'+checkNo).focus(); 
	}
}</script>