how can i send web/desktop notification for others?

i want to send desktop notification for my website visitor after the close my website

how can i make them subscribe ? and how to send the notification for them all

this website make the same jeapie.com, but i want to make my own

i have seen some code but it send notification for me only

if (event.target.id === 'button-wn-show-preset') {
  // Uses the preset parameters
} else {
  // Uses the custom parameters
}