我记得有不少开源仓库可以做个功能,不过我很长时间没做这方面的需求,所以暂时想不起来。 如果自己开发的话,应该用 [`IntersectionObserver`](https://link.segmentfault.com/?enc=YMnY7BCTKd7ZaFIsU9NGPw%3D%3D.vaLeYcsgAOWxwFhsy%2F1WFOb6Qxp7OMpCkrCKHeH1dTkvDpcxuKJHZteL35WBcfSS30p3k%2BPkyzf%2B49vak2e6CUpC%2BJA%2BCiLuB%2Fq5otKPRzI%3D)。我之前写过一篇博客,可供参考:[Intersection Observer 笔记](https://link.segmentfault.com/?enc=IucUM%2Bop%2FzQr4RxpTXgPUw%3D%3D.%2FMJMmeaxl3N6OAM7fqIr%2Fr8T6E78wVSC3OGxCY%2FtaJ4X24n0GGaPuqltuKn4XOUHH2NencmwFw9uqMrY%2BEHPkk6BLbt9HU1a3rzcJ8hmw3g%3D)。