A map showing concerts in an area. Concerts are fetched from Songkick, the map is made with Mapbox GL.
Songkick requires all users of their API to apply for an API key. You can do so at songkick.com/developer. Beware this might take about 2 weeks, even though they say it should only take 7 days.
To use Mapbox you need an access token, which you get when you register at mapbox.com. It's free and gives you access to Mapbox Studio, statistics about map views and other stuff.
Once you have the keys, create a file called api-keys.js in the js folder that looks like this
var MAPBOX_ACCESS_TOKEN = 'my_mapbox_access_token';
var SONGKICK_API_KEY = 'my_songkick_api_key';
And you're off!