Marko is a JavaScript based reactive, UI-component library from eBay. It allows you to create modern web-applications in a declarative way. Launched in 2017, Marko is currently on version 5. At the time of this writing, it has 10.2K stars on GitHub. Marko allows you to create components in a single file, as well as you can choose to split the components in multiples files out-of-the-box. You can also define your components in a Jade-like concise syntax.