JavaScript before leaving the page

Question

I want to make a confirmation before user leaving the page. If he says ok then it would redirect to new page or cancel to leave. I tried to make it with onunload

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Answer 1

Most of the solutions here did not work for me so I used the one found here

I also added a variable to allow the confirm box or not

window.hideWarning = false;
window.addEventListener('beforeunload', (event) => {
    if (!hideWarning) {
        event.preventDefault();
        event.returnValue = '';
    }

});