倒计时

function Countdown(seconds) {

this._seconds = seconds;

}

Countdown.prototype._step = function() {

console.log(this._seconds);

if (this._seconds > 0) {

this._seconds -= 1;

} else {

clearInterval(this._timer);

}

};

Countdown.prototype.start = function() {

var _this=this;

_this._step();

_this._timer = setInterval(function() {

_this._step();

}, 1000);

};

new Countdown(10).start();