JavaScript set onbeforeunload to default

Question

In my web game,
I want to use onbeforeunload function to alert users that their game won't be saved. But when they click on the leave button, I don't want to show them this again, so I want to set onbeforeunload to default function without alertbox. What should I do?

Answer 1

Jakob Meier document.body.onbeforeunload = function (){
return false;
};
function clicked_leaving(){
/*I want to prevent alert here*/
}

Answer 2

Jakob Meier thank you so much👍

Answer 3

Implements something like an "once decorator" pattern with closures to abstract behaviour in any part of code...

const once = (fn, ctx=null, ...args) => {
let visited = !1;
return (event) => {
if (visited) {
event.preventDefault();
return;
}
// in other case, invoke!
visited = !0;
return fn.apply(ctx, [event, ...args]);
};
};

You can also remove the listener as part of execution:

https://developer.mozilla.org/en-US/docs/Web/API/BeforeUnloadEvent

window.addEventListener("beforeunload", function handler(event) {
// Cancel the event as stated by the standard.
event.preventDefault();
// Older browsers supported custom message
event.returnValue = 'You have unsaved work. Continue?';
// do more work above...
}, {
// auto unregister after execute
once: true
});

Answer 4

you could declare a variable like seen_alert = false and if they are shown the alert it is being set to true and then you check in your onbeforeunload
if(seen_alert){
//don't show alert
} else {
//show_alert
seen_alert=true
}

Maybe you could publish the piece of code this is about, for me to understand it better

Answer 5

yeah you could totally do:
var leaving = false;
and then in your unload event I think you do
document.body.onbeforeunload = function (event) {
if(leaving) {
//save game
//don't show alert
} else {
//game not saved
event.preventDefault();
//show alert
}
}