Twitter bootstrap 3.0 icon change on collapse

Question

This is about Bootstrap 3.0. I would like the icon/glyphicon to change on collapse. I.e, from a closed folder to an open one.

I have searched far and wide, and have

Answer 1

This is a CSS-based solution that relies on the default bootstrap.js collapse implementation. No additional HTML markup required (feel free to replace Font-Awesome with glyphicons, of course).

DEMO (Bootstrap 3.3.7):

DEMO (Bootstrap 4.0 / Font Awesome 5 CSS):