不想每次用倒计时，都现写代码，比较烦，这里记一下，也顺便分享一些倒计时简单的逻辑。
如果你有更简单方便的代码，可以分享给大家。
var method = {
countdownObj: {
timer: null,
time: 0,
changeTime: 0,
},
countdown: function(long, back) {
var that = this;
if (that.countdownObj.timer) {
clearInterval(that.countdownObj.timer);
}
that.countdownObj.time = long;
that.countdownObj.changeTime = long;
back(that.countdownObj.changeTime);
that.countdownObj.timer = setInterval(function() {
that.countdownObj.changeTime–;
back(that.countdownObj.changeTime);
if (that.countdownObj.changeTime < 1) {
clearInterval(that.countdownObj.timer);
}
}, 1000);
}
};
methods.countdown(60,function(time){
console.log(time);
});
函数里第一个数字是到时间长度，第二个回调函数，回传的 time 就是当前时间。