[Vuejs]-Bootstrap, popper.js and vue.js

Okay mate so if you use Bootstrap 4 you need to include Popper.js

https://getbootstrap.com/docs/4.0/getting-started/introduction/#js

Many of our components require the use of JavaScript to function.
Specifically, they require jQuery, Popper.js, and our own JavaScript
plugins.

And remember jQuery first, then Popper.js, then Bootstrap JS