About 60-70 minutes for the core (auto-focus, backspace, paste, numeric filter, completion check, CSS). Use the remaining time for bonus features and testing. The OTP input is usually simpler than a food ordering app, so 60-70 minutes should be enough.
Build the core first (auto-focus, backspace), then add paste support (often forgotten), numeric-only filter, completion detection (enable verify button), CSS with focus styling, and bonus features (arrow keys, error state, resend, accessibility) if time permits.
Paste support. Many candidates build auto-focus and backspace but forget that users copy the OTP from an email or SMS and paste it. Implementing paste support shows attention to detail and real-world thinking.
Arrow key navigation, error state (red border on invalid OTP), resend OTP with a countdown timer, auto-fill from SMS (autocomplete='one-time-code'), and accessibility (aria-label, role, screen reader announcements).
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