Ionic collapse - collapsable list

I found a perfect solution for collapsible list but i’m learning ionic for just 6 days now…and i don’t know where to put this.

https://codepen.io/shengoo/pen/bNbvdO/

i know i could put it directly on my page…but that is not the right way…
where does the custom css and javasript go?

I figure you have looked over the tutorial project from the Documentation. If not, first do that: http://ionicframework.com/docs/v2/getting-started/tutorial/

Now, this is not required, but as the tutorial states it is best practice: create a new folder for your page and put the corresponding html, css and js files there. Lastly, import your css file to the core scss file found in app/theme/app.core.scss . Just add this to the file:

@import "path/to/your/file";

Hope this helps!