en.javascript.info/2-ui/3-event-details/3-mousemove-mouseover-mouseout-mouseenter-mouseleave/2-hoverintent/solution.md

The algorithm looks simple:

1. Put onmouseover/out handlers on the element. Also can use onmouseenter/leave here, but they are less universal, won't work if we introduce delegation.
2. When a mouse cursor entered the element, start measuring the speed on mousemove.
3. If the speed is slow, then run over.
4. When we're going out of the element, and over was executed, run out.

But how to measure the speed?

The first idea can be: run a function every 100ms and measure the distance between previous and new coordinates. If it's small, then the speed is small.

Unfortunately, there's no way to get "current mouse coordinates" in JavaScript. There's no function like getCurrentMouseCoordinates().

The only way to get coordinates is to listen to mouse events, like mousemove, and take coordinates from the event object.

So let's set a handler on mousemove to track coordinates and remember them. And then compare them, once per 100ms.

P.S. Please note: the solution tests use dispatchEvent to see if the tooltip works right.