Examples for generating 'Stable, Predictable and Unique' keys

Reconciliation chapter spends a good time explaining why using the index or even Math.random() as a key is a bad idea, proceeding to suggest using an existent id as a key. When there's not an existent id, it's suggested to "add a new ID property to your model or hash some parts of the content to generate a key".

That's a very controversial issue, a lot of people do it wrong. An example of how to do it would make the chapter a lot better. It's an extensive chapter (compared to others) that seems to end up with no code conclusion. 

Empieza leyendo la sección "Recursing On Children" del capítulo Reconciliation y la discusión enlazada sobre la generación de claves únicas. Determina un ejemplo claro y técnicamente sólido para modelos sin una id existente y, después, actualiza ese capítulo con el ejemplo y la explicación; la tarea estará terminada cuando la guía aborde los errores comunes sin depender de claves inestables.