Skillintermediate

rerender memo with default value

title: Extract Default Non-primitive Parameter Value from Memoized Component to Constant impact: MEDIUM impactDescription: restores memoization by using a constant for default value tags: rerender, memo, optimization

Claude Code Knowledge Pack7/10/2026

Overview

Extract Default Non-primitive Parameter Value from Memoized Component to Constant

When memoized component has a default value for some non-primitive optional parameter, such as an array, function, or object, calling the component without that parameter results in broken memoization. This is because new value instances are created on every rerender, and they do not pass strict equality comparison in memo().

To address this issue, extract the default value into a constant.

Incorrect (onClick has different values on every rerender):

const UserAvatar = memo(function UserAvatar({ onClick = () => {} }: { onClick?: () => void }) {
  // ...
})

// Used without optional onClick

Correct (stable default value):

const NOOP = () => {};

const UserAvatar = memo(function UserAvatar({ onClick = NOOP }: { onClick?: () => void }) {
  // ...
})

// Used without optional onClick