React Performance: JS Perf — Combine Iterations. Keywords: combine filter map loop. Platform: React/Next.js. Description: Combine multiple filter/map into single loop. Do: Single loop for multiple categorizations. Don't: Chain multiple filter() calls. Good Example: for (u of users) { if (u.isAdmin) admins.push(u); if (u.isTester) testers.push(u) }. Bad Example: users.filter(admin); users.filter(tester); users.filter(inactive). Severity: Low-Medium.