Checkpoints - Do not use a down event on a web page
Down events on a page such as mousedown, onmousedown or mouseDown() should not be used on a page, instead any action should be tied to the up event. This is because people with various disabilities can inadvertently initiate touch or mouse events with unwanted results. Also binding it to the up event means that users can move away from a button that is half clicked (pushed down) and release next to the button, which means the button is not activated.
Accessibility (WCAG 2.1, 2.5.2)
This checkpoint should flag cases where: .mousedown, or mouseDown() is used in the sourcecode of the page