How to click on an element, move the mouse over other elements and then select those elements that you hovered over with JavaScript?

I am basically trying to replicate the .selectable() method of jQuery but I need it in vanilla JavaScript. Which event listener method should I use? I've tried with mousedown, but how can I detect that another element has been visited? Here is an example on how jQuery does it: [http://jsfiddle.net/ZfevM/99/]

I was able to figure it out. Had to work with mouseup and mousemove as well. Here is what I came up with and it works as expected: [https://repl.it/repls/EquatorialLumberingInfinity]

Any thoughts or alternative solutions are welcomed!