when press back button, safari will navigate to the page that is same as when we leave, we don't want that, use this code!

window.onpageshow = function(event) {
    if (event.persisted) {
        window.location.reload() 
    }
};

from : https://stackoverflow.com/questions/8788802/prevent-safari-loading-from-cache-when-back-button-is-clicked