Does Mithril 2.x Reset Component State When Key Changes Across Routes?

Goal

To understand how Mithril 2.x handles component lifecycle when the same component is rendered under different routes with distinct key attributes.

Context

Mithril 2.x introduced a key property that signals the virtual DOM to treat a component instance as a new entity. When a component is rendered with a new key, the diffing algorithm detaches the old virtual node and mounts a fresh one, which triggers oncreate again. However, the framework documentation does not clarify whether internal component state (e.g., properties set in oninit or data bindings) is reset or preserved after a key change. In Mithril 1.x, the same component would not be re‑created on key change, leading to a compatibility gap for projects upgrading to 2.x.

Unresolved Decision

Is the internal state of a component cleared automatically when its key changes, or does Mithril preserve it across route transitions?

Specific Questions

• Which part of Mithril’s diffing algorithm determines whether internal component state is reset when a key changes?
• Does changing the key on a component that is reused across routes cause oncreate to fire again in all current 2.x releases?