react-doctor/js-index-maps

Build an index `Map` once outside the loop instead of `array.find(...)` inside it

• Category: Performance
• Severity: warn
• Source: oxlint-plugin-react-doctor
• Framework: global
• Enabled when: always

Validation prompt

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The rule fires on array.find(...) or array.findIndex(...) inside any loop body (uses createLoopAwareVisitors). False positive when the searched array changes per iteration (so a pre-built index can't be reused), or when the array is tiny (< ~10 items) where linear scan beats Map allocation and hashing overhead.

Fix prompt

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Before the loop, build const byId = new Map(items.map(item => [item.id, item])); then use byId.get(targetId) inside — O(1) lookups turn the total cost from O(n*m) into O(n+m). For multi-key lookups, build several Maps or a Map keyed on a composite string. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Map