Overview

Some configuration options and item properties admit templates. Custom Sidebar admits two templating systems, JavaScript templates or Jinja templates. JavaScript templates are processed faster because the rendering is done in client side, Jinja templates need to perform a WebSocket call to receive the template result, but in general you should not notice many differences between the two in terms of performance. The main differences between the two templating systems (apart from the syntax) are that JavaScript can access client side data like DOM APIs, can return Promises and can work with Reactive JavaScript Variables. Jinja templates are mostly agnostic to the device in which Home Assistant is being executed, cannot return Promises and do not support reactive variables.