yup

Yup - Quick Reference

Full Reference: See advanced.md for conditional validation (.when), custom validation (.test), Formik/React Hook Form integration, transforms, and localization.

Deep Knowledge: Use mcp__documentation__fetch_docs with technology: yup for comprehensive documentation.

Setup

npm install yup

Basic Usage

import * as yup from 'yup';

const userSchema = yup.object({
  name: yup.string().required().min(2).max(50),
  email: yup.string().required().email(),
  age: yup.number().required().min(18).max(120).integer(),
  bio: yup.string().optional(),
});

// Type inference
type User = yup.InferType<typeof userSchema>;

// Validate
async function validateUser(data: unknown) {
  try {
    const user = await userSchema.validate(data, { abortEarly: false });
    return { success: true, data: user };
  } catch (error) {
    if (error instanceof yup.ValidationError) {
      return { success: false, errors: error.errors };
    }
    throw error;
  }
}

Schema Types

String

const stringSchema = yup
  .string()
  .required('Name is required')
  .min(2, 'Too short')
  .max(100, 'Too long')