Bootbox
Bootbox.js is a small javaScript library which allows you to create programmatic dialog boxes using bootstrap modals, without having to worry about creating, managing or removing any of the required DOM elements or JS event handlers.
Examples
Work with nifty effects
Sweet Alert

Sweet alert styles
Here’s a comparison of a standard error message. The first one uses the built-in alert-function, while the second is using sweetalert. sweetalert automatically centers itself on the page and looks great no matter if you're using a desktop computer, mobile or tablet. It's even highly customizable, as you can see below!
A warning message, with a function attached to the "Confirm" button :
Passing a parameter, you can execute something else for "Cancel".