var?time?=?3;//s
var?start?=?window.setInterval(function(){
time?=?time?-?1;
console.log(time);
document.getElementById('show').innerHTML='計時開始，'+time+'秒後跳轉!';
if(time?==?0){
window.clearInterval(start);
document.getElementById('show').innerHTML='計時結束';
}
},1000);
}