Understanding Zod in 2 Minutes: Schema Validation in TypeScript

1import { z } from 'zod';
2
3// Simple schema definition
4const userSchema = z.object({
5  name: z.string().min(2, 'Name must contain at least 2 characters'),
6  age: z.number().min(18, 'User must be an adult'),
7  email: z.string().email('Invalid email format'),
8});
9
10// Type inferred automatically!
11type User = z.infer<typeof userSchema>;
12
13// Data validation
14const validateUser = (data: unknown) => {
15  const result = userSchema.safeParse(data);
16  return result.success ? result.data : result.error.issues;
17};

1const formSchema = z
2  .object({
3    type: z.enum(['individual', 'business']),
4    taxId: z.string().optional(),
5  })
6  .refine((data) => !(data.type === 'business' && !data.taxId), {
7    message: 'Tax ID is required for businesses',
8  });

1const dateSchema = z.string().transform((str) => new Date(str));
2const numberSchema = z.string().transform(Number);

1const result = userSchema.safeParse(data);
2if (!result.success) {
3  console.log(result.error.issues);
4  return;
5}
6// Use result.data safely

1const addressSchema = z.object({
2  street: z.string(),
3  city: z.string(),
4  zipCode: z.string().regex(/^\d{5}$/),
5});
6
7const userSchema = z.object({
8  // ...other fields
9  address: addressSchema,
10});

1const apiResponseSchema = z.object({
2  status: z.number(),
3  data: z.array(userSchema),
4  metadata: z.record(z.string()),
5});
6
7async function fetchUsers() {
8  const response = await fetch('/api/users');
9  const data = await response.json();
10
11  const result = apiResponseSchema.safeParse(data);
12  if (!result.success) {
13    throw new Error('Invalid API response');
14  }
15
16  return result.data;
17}

1const loginSchema = z.object({
2  email: z.string().email(),
3  password: z.string().min(8),
4});
5
6function handleSubmit(formData: unknown) {
7  const result = loginSchema.safeParse(formData);
8  if (!result.success) {
9    // Display errors
10    return;
11  }
12  // Process validated data
13}