Moving state down

React chapter 89 · Advanced React · ch.1 · source: Nadia Makarevich, Advanced React, Chapter 1 (re-renders)

The problem

A search box and a heavy catalog share one parent. Typing is local to the input, but the parent owns the query, so every keystroke re-renders the catalog. memo on the list is the heavy fix for a composition bug.

The pattern that fixes it

Put state in the smallest component that needs it. Extract the input. The catalog is now a sibling of that state, not a child of it, so it sits still while you type. Memo is optional after that.

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