Class is never declared in the markup of a page; it is strictly a worker object that performs background tasks.

类决不会在网页的标记中声明，严格地讲，它是一个执行后台任务的工作者对象。

youdao

Class is never declared in the markup of a page; it is strictly a worker object that performs background tasks.

类决不会在网页的标记中声明，严格地讲，它是一个执行后台任务的工作者对象。

youdao