crafting (and) JavaScript

<details> HTML element

Click below to see the code which creates this kinda dropdown, it is the <details> element.

A <details> code example (click here)
            <summary>A &lt;details&gt; code example (click here)</summary>
            ... too much recursion ... ;)

The <details> element "creates a disclosure widget in which information is visible only when the widget is toggled into an "open" state" MDN says.