首先我们先看一段代码,这是一个实现倒数功能的类「Countdown」及其实例化的过程:
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 = funct