How can I validate TypeScript types at runtime?

How can I validate TypeScript types at runtime?

In TypeScript, types are erased at runtime, so you can't directly validate them. However, you can use libraries like io-ts or zod to define runtime type validation.

Can you show me an example using zod?

Sure! Here's a simple example:

import { z } from 'zod';

const UserSchema = z.object({
  name: z.string(),
  age: z.number().min(0),
});

const result = UserSchema.safeParse({ name: 'Alice', age: 25 });
if (result.success) {
  console.log('Valid user:', result.data);
} else {
  console.log('Validation errors:', result.error);
}

What happens if the validation fails?

If the validation fails, safeParse will return an object with a success property set to false, and the error property will contain details about what went wrong.