car/assets/script/game/count_time_start.ts

import { _decorator, Component, Label, Node } from 'cc';
const { ccclass, property } = _decorator;

@ccclass('count_time_start')
export class count_time_start extends Component {
    @property(Node) lab_time:Node = null
    private count:number = 0;
    public startGame(num:number,cb:Function){
        this.count = num
        this.lab_time.getComponent(Label).string = this.count + ""
        this.lab_time.active = true
        this.schedule(()=>{
            if(this.count<=0){
                cb()
                this.lab_time.active = false
                this.unscheduleAllCallbacks()
            }
            this.lab_time.getComponent(Label).string = this.count + ""
            this.count--;
        },1)
   }
}