//定義getByClassName函數(shù)，讓函數(shù)實(shí)現(xiàn)根據(jù)class?name獲取對象并返回
	function?getClassName(obj,cls){
	????var?elements=obj.getElementsByTagName("*");
	????var?result=[];
	????for(var?i=0;i<elements.length;i++){
	????????result.push(elements[i]);
	????}
	????return?result;
	}
	
	function?hasClass(?obj,?cls?){?
	????return?obj.className.match(new?RegExp("(\\s|^)"?+?cls?+?"(\\s|$)"));
	}
	
	function?removeClass(?obj,?cls?){?
	????if(?hasClass(?obj,?cls?)){?
		????//remove
			var?reg?=?new?RegExp("(\\s|^)"?+?cls?+?"(\\s|$)");
			obj.className?=?obj.className.replace(reg,?"");
		}
	}
	
	
????//定義getByClassName函數(shù)，讓函數(shù)實(shí)現(xiàn)給對象增加class?
????function?addClass(obj,cls){
????????if(!hasClass(obj,cls)){
????????????obj.className+="?"+cls;
????????}
????}
	
	window.onload?=?function(){?
		
	????window.onscroll?=?function(){?		
		????var?top?=?document.documentElement.scrollTop?||?document.body.scrollTop;
			
			var?menus?=?document.getElementById("menu").getElementsByTagName("a");
			
			var?items?=?getByClassName(document.getElementById("content"),?"item");
			
			var?currentId?=?"";
			
			for?(?var?i=0;?i<?items.length;?i++?){?
			????var?_item?=?items[i];
			????var?_itemTop?=?_item.offsetTop;
				if(?top?>?_itemTop?-?200?){?
				????currentId?=?_item.id;
				}?else?{?
				????break;
				}			
			}
		
			?				
??????//請補(bǔ)充此處代碼，給正確的menu下的a元素class賦值current
??????if(currentId){
??????????for(var?j=0;j<menus.length;j++){
??????????????var?_menu=menus[j];
??????????????var?_href=_menu.href.split("#");
??????????????if(_href[_href.length-1]!=currentId){
??????????????????removeClass(_menu,"current");
??????????????}else{
??????????????????addClass(_menu."current");
??????????????}
??????????}
??????}
??????
	
		}	
	}