I use localStorage.setItem() to store user data for long period, Yesterday and my free account has been deactivated. I send support ticket to reactivate my account to infinityfree and they reactivated my account, but the file in which I use localStorage.setItem() was removed.
My main question is this that localStorage function is allowed or not.
localStorage is and inappropriate method to store Session Data especially from Javascript. Saving sensitive user data in localStorage from JS is an unsecure method of storing data. If you are seeking to store data, use the PHP $_SESSION instead.
LocalStorage is a Javascript feature implemented in web browsers. There is no server interaction whatsoever, so there is nothing we can do to allow or block the use of local storage on websites we host.
So, to answer your question: yes, it’s allowed. You’re free to use any Javascript functionality on your website, including LocalStorage.