How to save user input data permanently into an array or any similar method. Data shouldn't be deleted after closing.

Answer 1

You can use Angular JavaScript, that's how @Burey does it.

Answer 2

You can use Local Storage or cookies, with either of them you can store data in user's browser:
https://www.w3schools.com/html/html5_webstorage.asp
https://www.w3schools.com/js/js_cookies.asp
or save them in databases, firebase etc.