function focus(tagId,conId,tabtn,contn){this.tabs=document.getElementById(tagId).getElementsByTagName(tabtn||'li');this.total=this.tabs.length;this.cons=document.getElementById(conId).getElementsByTagName(contn||'img');if(this.cons.length!=this.total){alert('出错啦，按钮数与要显示的元素数目不匹配');return;}
this.current=0;var obj=this;for(i=0;i<this.total;i++){(function(){var b=i;obj.tabs[i].onclick=function(){obj.current=b;clearTimeout(obj.run);obj.run=setTimeout(obj.start,10);}})();}
(this.start=function(){if(obj.current>=obj.total)obj.current=0;for(i=0;i<obj.total;i++){obj.tabs[i].className=(obj.current==i)?'current':'';obj.cons[i].style.display=(obj.current==i)?'block':'none';}
obj.current++;obj.run=setTimeout(obj.start,7000)})();}