Работа с API и внешними данными

async function getUser(id: number) {
    const res = await fetch(`/api/users/${id}`);
    return res.json(); // Promise<any>
}

async function getUser(id: number): Promise<User> {
    const res = await fetch(`/api/users/${id}`);
    return res.json() as Promise<User>;
}

type User = {
    id: number;
    name: string;
    email: string;
};

function isUser(value: unknown): value is User {
    return (
        typeof value === 'object' &&
        value !== null &&
        'id' in value &&
        typeof (value as User).id === 'number' &&
        'name' in value &&
        typeof (value as User).name === 'string'
    );
}

async function getUser(id: number): Promise<User> {
    const res = await fetch(`/api/users/${id}`);
    const data: unknown = await res.json();

    if (!isUser(data)) {
        throw new Error('Invalid user data');
    }

    return data;
}

import { z } from 'zod';

const UserSchema = z.object({
    id: z.number(),
    name: z.string(),
    email: z.string().email(),
});

type User = z.infer<typeof UserSchema>;

async function getUser(id: number): Promise<User> {
    const res = await fetch(`/api/users/${id}`);
    return UserSchema.parse(await res.json());
}

const PostSchema = z.object({
    id: z.number(),
    title: z.string().min(1),
    tags: z.array(z.string()),
    published: z.boolean().optional(),
    createdAt: z.string().datetime(),
});

type Post = z.infer<typeof PostSchema>;

const AddressSchema = z.object({
    city: z.string(),
    zip: z.string(),
});

const UserSchema = z.object({
    name: z.string(),
    address: AddressSchema,
});

const ShapeSchema = z.discriminatedUnion('kind', [
    z.object({ kind: z.literal('circle'), radius: z.number() }),
    z.object({ kind: z.literal('square'), side: z.number() }),
]);

const DateSchema = z.string().transform((s) => new Date(s));

const result = UserSchema.safeParse(data);

if (result.success) {
    console.log(result.data); // User
} else {
    console.log(result.error.issues);
}