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// Compile once, use many times (avoid re-creating in loops) const emailPattern = /^[^\s@]+@[^\s@]+\.[^\s@]+$/; function validateEmail(email) { return emailPattern.test(email); } // Catastrophic backtracking example to avoid: // /^(a+)+$/ against "aaaaaaaaab" — exponential time // Safer alternative using atomic groups or possessive quantifiers // Not natively in JS — use workarounds or libraries // Test with large strings in dev to catch slow patterns
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