该函数会判断元素是否已经高亮显示了类名，并根据查找结果执行添加或删除。

This function then determines if the element already has the class name highlight, and removes or adds based on its findings.

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用户是否通过状态条、指针的变化或高亮显示的改变注意到信息的下载？

Will users notice that message down in the status bar, or the cursor change, or the highlight change?

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