var i = 5;
function init(){
//獲得對(duì)象的控制權(quán)
var span1 = document.getElementById("span1");
//修改其屬性
span1.innerHTML = i;
i--;
//定時(shí)的操作：window.setTimeout('',1000) window.setInterval();
window.setTimeout('init()', 1000);
}