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Arka Chakraborty
Arka Chakraborty

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Do You Always Need to Throw Errors in never Exhaustive Checks? (React + TSX Guide)

#react #typescript #javascript #webdev

Whether Throwing an Error Is Mandatory in Exhaustive Checks

đź“ť Context

A common misconception: nevermeans you must throw an error in default. Not true-you can choose how to handle it.

🚨 Without TypeScript – The Problem

function Page({ route }) { switch (route) { case "home": return <p>Home</p>; case "about": return <p>About</p>; // ❌ "contact" forgotten default: return null; // silently ignores } }
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✅ With TypeScript + never – Alternatives

type Route = "home" | "about" | "contact"; function Page({ route }: { route: Route }) { switch (route) { case "home": return <p>Home</p>; case "about": return <p>About</p>; case "contact": return <p>Contact</p>; default: { const _exhaustive: never = route; // Options instead of crash: console.error("Unexpected route:", route); return <p>Redirecting...</p>; // Or: toast("Invalid route"); // Or: navigate("/home"); } } }
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🎯 Takeaway

  • neverenforces exhaustiveness, but how you handle it is up to you.
  • Options: return fallback UI, log error, redirect, show toast.

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