make example suitable for teenagers/children!?

Maybe that's quite a conservative attempt.
The [*Check for spam* chapter of *Strings*](https://javascript.info/string#check-for-spam) has an example that uses *viagra* and *XXX*.

Considering that nowadays also many young people learn coding on JavvaScript.info I'd personally consider it more suitable (aka. inclusive) for all ages to simple use a different topic that's not so adult-ish.

What do you think?

从 Strings 章节中链接的“Check for spam”部分开始，检查当前示例。选择一个非成人主题，同时保留示例的用途，更新示例，并确认该章节对年轻读者仍然清晰易懂。

由索引模型根据 Issue 内容生成。