A tree view (collapsible list) can be created using only html and css, without the need for JavaScript. Accessibility software will see the tree view as lists nested inside disclosure widgets, and the standard keyboard interaction is supported automatically.

For a recent New York Times article, I wanted to see if it was possible to create SVG charts that would work without JS.
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At the New York Times we're using a very similar technique to create JS-less maps tracking the coronavirus outbreak.