react runtime_error ai_generated true

Warning: React.memo: The comparison function returned true for props that are not equal. This may cause the component to skip rendering when it should update.

ID: react/memo-wrong-comparison

Also available as: JSON · Markdown · 中文
90%Fix Rate
85%Confidence
1Evidence
2023-08-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
React 16.6+ active — — —
React 17.x active — — —
React 18.x active — — —

Root Cause

A custom comparison function passed to React.memo incorrectly returns true (equal) for props that are actually different, causing the component to skip re-renders when it should update.

generic

中文

传递给 React.memo 的自定义比较函数对实际上不同的 props 错误地返回 true（相等），导致组件在应该更新时跳过了重新渲染。

Official Documentation

https://reactjs.org/docs/react-api.html#reactmemo

Workarounds

  1. 92% success Fix the comparison function to correctly compare all relevant props. Example: const MyComponent = React.memo(Comp, (prevProps, nextProps) => { return prevProps.id === nextProps.id && prevProps.name === nextProps.name; }); Ensure it returns false when props differ. 
    Fix the comparison function to correctly compare all relevant props. Example: const MyComponent = React.memo(Comp, (prevProps, nextProps) => { return prevProps.id === nextProps.id && prevProps.name === nextProps.name; }); Ensure it returns false when props differ.
  2. 88% success If the component relies on deep equality, use a library like lodash.isEqual for the comparison: import isEqual from 'lodash.isequal'; React.memo(Comp, isEqual); 
    If the component relies on deep equality, use a library like lodash.isEqual for the comparison: import isEqual from 'lodash.isequal'; React.memo(Comp, isEqual);
  3. 80% success Remove the custom comparison function and let React.memo use default shallow comparison, but ensure props are immutable references. 
    Remove the custom comparison function and let React.memo use default shallow comparison, but ensure props are immutable references.

中文步骤

  1. Fix the comparison function to correctly compare all relevant props. Example: const MyComponent = React.memo(Comp, (prevProps, nextProps) => { return prevProps.id === nextProps.id && prevProps.name === nextProps.name; }); Ensure it returns false when props differ.
  2. If the component relies on deep equality, use a library like lodash.isEqual for the comparison: import isEqual from 'lodash.isequal'; React.memo(Comp, isEqual);
  3. Remove the custom comparison function and let React.memo use default shallow comparison, but ensure props are immutable references.

Dead Ends

Common approaches that don't work:

  1. 70% fail

    Shallow comparison may still miss deep changes, and the warning indicates the custom function is buggy, not that shallow is better.

  2. 85% fail

    JSON.stringify is slow and can produce false positives for object key order; also triggers the same warning if not careful.

  3. 65% fail

    Defeats the purpose of memoization and may cause performance issues, but does not fix the underlying logic error.