How can I implement validation in React Final Form?

How can I implement validation in React Final Form?

You can implement validation in React Final Form by using the validate prop in your form component. This prop accepts a function that checks the values and returns an object with error messages.

Can you show me an example of a validation function?

Sure! Here's a simple example:

const validate = values => {
  const errors = {};
  if (!values.email) {
    errors.email = 'Required';
  } else if (!/\S+@\S+\.\S+/.test(values.email)) {
    errors.email = 'Invalid email address';
  }
  return errors;
};

How do I connect this validation function to my form?

You can connect it by passing the validate function to your Form component like this:

<Form
  onSubmit={onSubmit}
  validate={validate}
>
  {/* form fields */}
</Form>

What if I want to validate multiple fields?

You can extend the validate function to check multiple fields by adding more conditions to the errors object for each field you want to validate.