为什么注释的不可以实现效果

var list=document.getElementsByTagName("li");
		/*for(i=0,len=list.length;i<len;i=i+2){
				if(i%2==0){
            list[i].setAttribute("class","pink")+list[i].setAttribute("id","purple"); 
        }
        else{
           list[i].setAttribute("class","orange")+list[i].setAttribute("id","yellow");
        	}
		}
		*/
		for (var i = 0; i < list.length; i++) {
    if (i % 2 == 0) { 
        list[i].setAttribute("id","purple");
        list[i].setAttribute("class", "pink");
    } else { 
        list[i].setAttribute("id", "yellow");
        lis[i].setAttribute("class", "orange");
    }
}