var host = window.location.host,
		splitDomainConfig = function(num,domainHost){
			var arr = domainHost.split("."),
				len = arr.length,
				array = [];
			
			if(num>len) return;
			
			for(var i = 0;i < num; i++){
				 array.push(arr[len-(i+1)]);
			 }
			return array.reverse().join('.');
		},
		
		getTopDomain = function(domainHost){
			if(!domainHost) return ;
			var domain = domainHost.substring(domainHost.lastIndexOf(".")+1, domainHost.length);
			if(!domain) return;
			
			if(domain == 'cn'){
				if(domainHost.indexOf("cc.cqust.edu.cn")!=-1){
 
					return "cc.cqust.edu.cn"
				}else if(domainHost.indexOf("moocs.jlu.edu.cn")!=-1){
					return "moocs.jlu.edu.cn";
				}
				else{
					return splitDomainConfig(3,domainHost);
				}
				
			}else{
				return splitDomainConfig(2,domainHost);
			}
		};
	
	try{
		
		if(window.parent==window){
			document.domain = getTopDomain(host);
		}else if(window.top.document.domain){
			
		}
	}catch(e){
		document.domain = getTopDomain(host);
	}