> the 3rd big gotcha of web components. Attributes are strings. You have to serialize and deserialize from strings. Sure you can listen to when they change via attributeChangedCallback and get immutability for free because of serialization, but that comes at a perf cost. for deeply nested objects, you have to serialize and deserialize from json.

In practice, most libraries built around web components only use attributes when serializing / deserializing HTML strings. When performing updates to existing DOM, it is very common for a library to use a corresponding property instead. This is very fast, supports all types of values, and many libraries enable users to think in terms of attributes while the library updates properties under the hood (conceptually similar to the React mental model).