如何为cocos2d创建倒计时器？

const { Label } = cc;
const { LabelOutline } = cc;

start() {
  this.timerLabel = new Label('60', { fontSize: 24 });
  this.timerLabel.setPosition(cc.v2(0, 0));
  this.addChild(this.timerLabel);
}

update(dt) {
  if (this.timer > 0) {
    this.timer -= dt;
    this.timerLabel.string = Math.floor(this.timer).toString();
  }
}

start() {
  this.timer = 60; // 设置倒计时的初始值为 60 秒
  this.timerLabel = new Label('60', { fontSize: 24 });
  this.timerLabel.setPosition(cc.v2(0, 0));
  this.addChild(this.timerLabel);
}

update(dt) {
  if (this.timer > 0) {
    this.timer -= dt;
    this.timerLabel.string = Math.floor(this.timer).toString();
  } else {
    // 倒计时结束时执行的操作
    this.gameOver();
  }
}