TL;DR
This article describes a way to gradually migrate shared Mithril components from version 0.2 to 1.x.
Documentation
Before we start, I have to say that Mithril has a great migration page which you should definitely check out before reading this article. There is even a tool named mithril-codemods which will automatically convert your code.
Context
Here is the context: you’ve written multiple applications with Mithril 0.2 and you have extracted some of your components as npm modules so that they can be shared among your projects. You are now starting a new project and you’d like to use Mithril 1.x. The question is: how do you structure your shared components so that they can be used by your new application written with Mithril 1.x and your other applications written with Mithril 0.2 ?