What are the best practices for using Formik with async validation?

What are the best practices for using Formik with async validation?

When using Formik with async validation, it's important to ensure that your validation function returns a promise. This allows Formik to handle the async nature of the validation properly.

Can you give me an example of an async validation function?

Sure! Here's a simple example:

const validateEmail = async (email) => {
  const response = await fetch(`/api/validate-email?email=${email}`);
  const data = await response.json();
  return data.isValid ? undefined : 'Email is already taken';
};

This function checks if the email is valid by making an API call.

How do I integrate this with Formik?

You can integrate it by passing the validation function to the validate prop in Formik. Here's how:

<Formik
  initialValues={{ email: '' }}
  validate={values => validateEmail(values.email)}
  onSubmit={handleSubmit}
>
  {/* Form components */}
</Formik>

What if I want to show a loading state while validating?

You can manage a loading state using Formik's setStatus method. Set a loading state before the async call and reset it afterward.