Currently nested dropdown works, but clicking inside the parent dropdown will not collapse any nested dropdown, even if collapseOnOutsideClick is set to true, because the parent elements prevents the default event. If a dropdown has mixed content (dropdowns and other controls), an expanded dropdown will not automatically collapse when other controls at the same nesting level are operated.
With the third level of nested dropdowns the plugin actually breaks with some specific options, and trying to expand the dropdown will instead lead to collapsing the parent dropdown.

Collapse drop down when an action which does not require a page redirect is performed. Useful for toolbars.

Describe the bug
When the page hasn't fully loaded, the dropdown menu can be visible.

To Reproduce
Steps to reproduce the behavior:

1. Load the demo page - https://davidetriso.github.io/aria-dropdown/
2. You can view the menu for a split second or two.

Expected behavior
The dropdown menu should not be visible unless it has focus.

Additional context
I have the following CSS fix in a testing environment:

.dropdown__menu {
  /* hide offscreen for accessibility */
  position: absolute;
  left:-10000px;
  top: auto;
  width: 1px;
  height: 1px;
  overflow: hidden;
}
/* show menu when expanded */
.dropdown__menu_expanded {
  left: auto;
  width: auto;
  height: auto;
  overflow: auto;
}

The "moving content offscreen" technique is from the WebAIM article - "Invisible Content Just for Screen Reader Users":
https://webaim.org/techniques/css/invisiblecontent/

I'm not sure if this is the proper technique for menus. CSS Tricks has the following article on dropdown menus:
https://css-tricks.com/solved-with-css-dropdown-menus/

They are using simply visibility: hidden and display: none. I don't necessarily think "display: none" is the best approach there. Would welcome your thoughts.

Also worth noting from the comments section of the CSSTricks article are the following attempts at addressing accessible dropdown menus:

• https://www.ajsaucier.com/accessibility/2018/06/13/accessible-keyboard-navigation.html
• https://github.com/Heydon/inclusive-menu-button (article explaining the approach)

Could be useful to manage dropdown state with mouse enter and mouse out on desktop.
If mousernter event is detected, block click event until mouseout occurs. By doing this it will be possible to prevent dropdown from collapsing on click for users with mouse. At the same time, the click functionality is preserved for users without mouse, and the dropdown will also be operable on touch devices.

iOS window click is not triggered, need to test on IE mobile and android

collapseOnOutsideClick has no effect on mobile iOS because no click event is fired when window is clicked.

Needs to implement touch events