How to add a class in a cycle only to the element with which the interaction is performed?

Question

Vue.js

When hovering over an element, the class changes for all elements ...
How, in this case, to add only to the element with the desired index?
There is an option to execute the method with vanilla JS there classList.addtoo, but this is not a true View way.

Answer 1

https://codepen.io/anon/pen/ZjvXEp