It outlines an article by making headings of a web page collapsed. It is useful when you reading papers, articles or documents with good structure. Well, it doesn't work well on every site. Because there are so many different web structures. To make it compliant, you can do slight change on the source code .I have made this source public, you can access it here(https://github.com/FrankZhai367/toggle-heading) 它能通过将标题可折叠化，给一篇网页文章添加大纲。当你在阅读新闻，文档，或者论文的时候这会很方便。当然它只适用于一些结构良好的网页，如果你想让它兼容你想要阅读的网站。你可以在这里更改代码做一些改动（https://github.com/FrankZhai367/toggle-heading）