js实现简单的轮播图效果

window.Onload= function() {
 //banner 自动播放
 var oBanner = document.getElementById('banner');
 var aLi = oBanner.getElementsByTagName('li');
 var oJumpBtn = document.getElementById('jumpBtn');
 var aBtn = oJumpBtn.getElementsByTagName('li');
 var oPreImg = document.getElementById('preImg');
 var OnexImg= document.getElementById('nexImg');
 var iNow = 0;
 var timer = null;
 for (var i = 0; i