carrot/assets/Script/SelectLevel.ts

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

@ccclass('SelectLevel')
export class SelectLevel extends Component {
    start() {
        let BtnStart = this.node.getChildByName("BtnStart");
        BtnStart.on(Button.EventType.CLICK,this.onBtnStart,this);
    }

    onBtnStart(){
        director.loadScene("MainScene");
    }
    update(deltaTime: number) {
        
    }
}