Help for onReady function

Hi! Thank you for your answer!
I try to use your code but maybe I don’t undertand what I have to do
Can you help me with an example, please?
This is one of my code inside my website:

export function tretorn_mouseIn ( event ) {
$w ( ‘#tretorn’ ). onMouseIn (() => { $w ( ‘#tretornimg’ ). show (); })
}
export function tretorn_mouseOut ( event ) {
$w ( ‘#tretorn’ ). onMouseOut (() => { $w ( ‘#tretornimg’ ). hide (); })
}