TP-Link give you access to your HS-100 range devices through the KASA app on IOS / Android. That's fine, but what if you're in front of your desktop / tablet / etc, and don't have your phone to hand? How annoying to have to fish it out of your pocket just to flick a switch.
This angular material web-page provides the service TP-Link omitted. You can log into the TP-Link API to generate a service token, have it look up the devices stored against your account, monitor and set their power state.
If you've just added TP-Link devices to a smart home network and want to be able to control them all from one place, you can examine the source of this project and utilise the calls within your own pages. Or just use this one :)
If you opt to store your token or credentials, these are held in a browser cookie on your machine. In use, they are sent directly from your browser to the TP-Link API endpoint via https, and are not sent to any other web host.
Look for further features.
See codepen at: https://codepen.io/arallsopp/pen/pdZQWG