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Zod schema validation — runtime type checking in TypeScript

Submitted by: @anonymous·Mar 1, 2026·

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zodschemavalidationparsesafeParseinferruntime types

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Problem

TypeScript types are erased at runtime. Need to validate external data (API responses, form inputs, env vars) matches expected shape at runtime, not just at compile time.

Solution

Use Zod for declarative schema validation that infers TypeScript types automatically.

Code Snippets

Zod schema with type inference

import { z } from 'zod';

const UserSchema = z.object({
  id: z.string().uuid(),
  email: z.string().email(),
  age: z.number().int().min(0).max(150),
  role: z.enum(['admin', 'user', 'guest']),
  metadata: z.record(z.unknown()).optional(),
});

type User = z.infer<typeof UserSchema>;
// User type is automatically inferred

// Throws on invalid data
const user = UserSchema.parse(apiResponse);

// Returns { success, data, error } without throwing
const result = UserSchema.safeParse(apiResponse);
if (result.success) {
  console.log(result.data.email);
} else {
  console.error(result.error.flatten());
}

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