| 1 | --- |
| 2 | title: Use toSorted() Instead of sort() for Immutability |
| 3 | impact: MEDIUM-HIGH |
| 4 | impactDescription: prevents mutation bugs in React state |
| 5 | tags: javascript, arrays, immutability, react, state, mutation |
| 6 | --- |
| 7 | |
| 8 | ## Use toSorted() Instead of sort() for Immutability |
| 9 | |
| 10 | `.sort()` mutates the array in place, which can cause bugs with React state and props. Use `.toSorted()` to create a new sorted array without mutation. |
| 11 | |
| 12 | **Incorrect (mutates original array):** |
| 13 | |
| 14 | ```typescript |
| 15 | function UserList({ users }: { users: User[] }) { |
| 16 | // Mutates the users prop array! |
| 17 | const sorted = useMemo( |
| 18 | () => users.sort((a, b) => a.name.localeCompare(b.name)), |
| 19 | [users] |
| 20 | ) |
| 21 | return <div>{sorted.map(renderUser)}</div> |
| 22 | } |
| 23 | ``` |
| 24 | |
| 25 | **Correct (creates new array):** |
| 26 | |
| 27 | ```typescript |
| 28 | function UserList({ users }: { users: User[] }) { |
| 29 | // Creates new sorted array, original unchanged |
| 30 | const sorted = useMemo( |
| 31 | () => users.toSorted((a, b) => a.name.localeCompare(b.name)), |
| 32 | [users] |
| 33 | ) |
| 34 | return <div>{sorted.map(renderUser)}</div> |
| 35 | } |
| 36 | ``` |
| 37 | |
| 38 | **Why this matters in React:** |
| 39 | |
| 40 | 1. Props/state mutations break React's immutability model - React expects props and state to be treated as read-only |
| 41 | 2. Causes stale closure bugs - Mutating arrays inside closures (callbacks, effects) can lead to unexpected behavior |
| 42 | |
| 43 | **Browser support (fallback for older browsers):** |
| 44 | |
| 45 | `.toSorted()` is available in all modern browsers (Chrome 110+, Safari 16+, Firefox 115+, Node.js 20+). For older environments, use spread operator: |
| 46 | |
| 47 | ```typescript |
| 48 | // Fallback for older browsers |
| 49 | const sorted = [...items].sort((a, b) => a.value - b.value) |
| 50 | ``` |
| 51 | |
| 52 | **Other immutable array methods:** |
| 53 | |
| 54 | - `.toSorted()` - immutable sort |
| 55 | - `.toReversed()` - immutable reverse |
| 56 | - `.toSpliced()` - immutable splice |
| 57 | - `.with()` - immutable element replacement |
| 58 |