Nicholai
75168f7678
structure: state/CURRENT.md — 2-4 line session state (rewritten each session) events/ — json event bus (pull-based, optional context) persistent/ — important decisions (one doc per decision) emit — helper script for emitting events
58 lines
1.7 KiB
Markdown
58 lines
1.7 KiB
Markdown
---
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title: Use toSorted() Instead of sort() for Immutability
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impact: MEDIUM-HIGH
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impactDescription: prevents mutation bugs in React state
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tags: javascript, arrays, immutability, react, state, mutation
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---
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## Use toSorted() Instead of sort() for Immutability
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`.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.
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**Incorrect (mutates original array):**
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```typescript
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function UserList({ users }: { users: User[] }) {
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// Mutates the users prop array!
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const sorted = useMemo(
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() => users.sort((a, b) => a.name.localeCompare(b.name)),
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[users]
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)
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return <div>{sorted.map(renderUser)}</div>
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}
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```
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**Correct (creates new array):**
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```typescript
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function UserList({ users }: { users: User[] }) {
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// Creates new sorted array, original unchanged
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const sorted = useMemo(
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() => users.toSorted((a, b) => a.name.localeCompare(b.name)),
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[users]
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)
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return <div>{sorted.map(renderUser)}</div>
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}
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```
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**Why this matters in React:**
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1. Props/state mutations break React's immutability model - React expects props and state to be treated as read-only
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2. Causes stale closure bugs - Mutating arrays inside closures (callbacks, effects) can lead to unexpected behavior
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**Browser support (fallback for older browsers):**
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`.toSorted()` is available in all modern browsers (Chrome 110+, Safari 16+, Firefox 115+, Node.js 20+). For older environments, use spread operator:
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```typescript
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// Fallback for older browsers
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const sorted = [...items].sort((a, b) => a.value - b.value)
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```
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**Other immutable array methods:**
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- `.toSorted()` - immutable sort
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- `.toReversed()` - immutable reverse
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- `.toSpliced()` - immutable splice
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- `.with()` - immutable element replacement
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