I use something that many people don't know about or aren't talking/posting about: JsRender/JsViews. https://www.jsviews.com

JsRender can be used client-side and server-side using Nodejs for rendering templates. JsViews adds observability (one-way or two-way) to JsRender on the frontend and requires jQuery (I like jQuery, it's overhead is minor ;-).

JsViews is intuitive, modular and extremely flexible and self-documenting in my opinion. JsViews does not include a router as there are so many different ways of doing routing and depends on your needs. The concept and syntax of converters is really cool too.