Cocos Creator 3.0 and Cocos Creator v2.x use a different syntax format.
Cocos Creator 3.0 has full support for ES6 and TypeScript. Therefore, Cocos Creator 3.0 only supports ES6 and TypeScript classes. In addition, we also support TypeScript syntax hints.
Cocos Creator supports only ES5 classes.
Please keep this precaution in mind.