One way is to build a web site. It can be about a hobby you enjoy, a fan site for a favorite something-or-other, or whatever is interesting enough to you that you'd actually be motivated to work on it. Then try to use current best practices and perhaps popular frameworks/libraries so that it shows off how you do things the "right" way. 😉
Another way to show you coding chops is to contribute to open-source projects on GitHub, and reference your pull requests, branches, whatever for any technical people who'd want to see your code.