知道一个绝对地址和一个相对地址，怎么得到这个相对地址的绝对地址

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 4{   
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 6var a = rPath.split("../");   
 7  
 8var p = a.length -1;   
 9  
10var s = aPath.substr(aPath.indexOf("//")+2);   
11  
12if(s.substr(s.length-1,1)=="/")   
13{   
14s = s.substr(0,s.length-1);   
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17for(var i = p;i>0;i--)   
18{   
19s = s.substr(0,s.lastIndexOf("/"));   
20}   
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22s = "http://" + s + "/";   
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24for(var j =0;j<a.length;j++)   
25{   
26s +=a[j];   
27}   
28  
29return s;   
30  
31}   
32  
33alert(getPath("http://eagleboost.myrice.com/issues/Materials/Articles/","../../../Comm.css"));   
34//-->   
35</script>