formik

What is formik?

Formik is a popular open-source library for building forms in React and React Native. It helps with handling form state, validation, and submission. Formik provides a simple and efficient way to create controlled form components with less boilerplate code.

What are formik's main functionalities?

Form State Management

Formik simplifies form state management by providing 'initialValues' to set up the form state and 'onSubmit' to handle form submission.

{"<Formik initialValues={{ name: '' }} onSubmit={(values) => { console.log(values); }}><Form><Field name='name' type='text' /><button type='submit'>Submit</button></Form></Formik>"}

Validation and Error Handling

Formik provides a 'validate' function to define custom validation logic and uses 'ErrorMessage' to display validation errors.

{"<Formik initialValues={{ email: '' }} validate={values => { const errors = {}; if (!values.email) { errors.email = 'Required'; } else if (!/^[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,}$/i.test(values.email)) { errors.email = 'Invalid email address'; } return errors; }} onSubmit={(values, { setSubmitting }) => { setTimeout(() => { alert(JSON.stringify(values, null, 2)); setSubmitting(false); }, 400); }}><Form><Field name='email' type='email' /><ErrorMessage name='email' component='div' /><button type='submit'>Submit</button></Form></Formik>"}

Integration with Yup for Schema Validation

Formik can be integrated with Yup, a schema builder for value parsing and validation, to simplify form validation using a schema.

{"<Formik initialValues={{ email: '' }} validationSchema={Yup.object({ email: Yup.string().email('Invalid email address').required('Required'), })} onSubmit={(values, { setSubmitting }) => { setTimeout(() => { alert(JSON.stringify(values, null, 2)); setSubmitting(false); }, 400); }}><Form><Field name='email' type='email' /><ErrorMessage name='email' /><button type='submit'>Submit</button></Form></Formik>"}

Custom Input Components

Formik allows the use of custom input components with the 'as' prop in the 'Field' component, enabling the creation of reusable form elements.

{"<Formik initialValues={{ name: '' }} onSubmit={(values) => { console.log(values); }}><Form><Field name='name' as={MyCustomInput} /><button type='submit'>Submit</button></Form></Formik>"}

Other packages similar to formik

react-hook-form

React Hook Form is a library for managing forms in React. It uses hooks for form state management and is optimized for performance by minimizing the number of re-renders. Compared to Formik, React Hook Form is often considered faster due to its leaner API and focus on reducing re-renders.

redux-form

Redux Form leverages Redux for form state management. It integrates tightly with Redux and allows form state to be stored in the Redux store. Compared to Formik, Redux Form is more suitable for applications that already use Redux and require complex form state management across multiple components.

final-form

Final Form is a framework-agnostic form library that can be used with React via 'react-final-form'. It focuses on performance and flexibility, offering subscription-based form state management. Compared to Formik, Final Form provides more fine-grained control over form state updates and subscriptions.

README

Formik

React Forms, done right.

Install

npm install formik --save

Usage

See example.

Author

• Jared Palmer @jaredpalmer