sajad torkamani

What is Yup?

Yup is a JavaScript schema builder library that lets you define a schema and then:

  • Transform values to match the schema (using cast()).
  • Validate the shape of a value against the schema (using validate()).

Yup separates the transformation and validation functions into two separate steps. But you can perform both functions together (e.g., in HTML form validation) or separately (e.g., when deserializing API data).

Basic usage

import * as yup from 'yup';

let schema = yup.object().shape({
  name: yup.string().required(),
  age: yup.number().required().positive().integer(),
  email: yup.string().email(),
  website: yup.string().url(),
  createdOn: () {
    return new Date();

// check validity
    name: 'jimmy',
    age: 24,
  .then(function (valid) {
    valid; // => true

// you can try and type cast objects to the defined schema
  name: 'jimmy',
  age: '24',
  createdOn: '2014-09-23T19:25:25Z',
// => { name: 'jimmy', age: 24, createdOn: Date }



mixed.cast(value: any, options = {}): any

This will attempt to cast the passed in value to a value that matches the schema. For example, '5' will be cast to 5 if using the number() type. Failed casts typically return null, but can also return results like NaN or unexpected strings.



mixed.validate(value: any, options?: object): Promise<any, ValidationError>

This is a asynchronous function that will return a different value depending on if validation passed or not:

  • Validation passed: Returns the value.
  • Validation failed: Returns ValidationError.

Example usage:

schema.validate({ name: 'jimmy', age: 24 }).then(function (value) {
  value; // => { name: 'jimmy',age: 24 }

schema.validate({ name: 'jimmy', age: 'hi' }).catch(function (err) {; // => 'ValidationError'
  err.errors; // => ['age must be a number']