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. Later if we're out of the element, and over was executed, run out.

The question is: "How to measure the speed?"

The first idea would be: to run our 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.

So we can set a handler on mousemove to track coordinates and remember them. Then we can compare them, once per 100ms.

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