Bootstrap is a css library. Now a days bootstarp is most common and very flexible to use in our web pages. we can use bootstrap css and js both. with the help of bootstap we can change our web pages design.beside of this we can use bootbox alert or other type of confirmations on our web pages. it is easy to use.
you can see the examples on below links :
Bootbox library : https://cdnjs.cloudflare.com/ajax/libs/bootbox.js/4.4.0/bootbox.min.js