This depends on what you're trying to showcase. If you want to showcase the visual design, then you could simply create a visual mock-up with a program like Sketch. If you want to showcase the User Experience, then designers typically mock-up the wireframes, and then use something like InVision to show how the flow of the interaction will work. If you know how to code and want to show a certain interaction (beyond simply linking mock-ups), then use coding to your advantage as this will prove or fail your idea best. Framer.js is also worth noting since it is a combination of a program like Sketch that allows you to use CoffeeScript to prototype more dynamic interactions.
If you're wondering about which is best to use for getting a job then... show code if you are applying for a developer role and design programs if you are applying for a design role.
Hope this helps.