Positively indicate valid input values Let users know a field has been entered correctly. The browser can give us this information through the :valid CSS selector:

Form Validation

return { type: "COUNTRY_BLACK_LIST", succeeded, message: succeeded ? "" : "This country is not available" }

It is easily extensible (already implemented Final Form and Formik plugin extensions).

Form validation can get complex (synchronous validations, asynchronous validations, record validations, field validations, internationalization, schemas definitions...). To cope with these challenges we will leverage this into Fonk and Fonk Final Form adaptor for a React Final Form seamless integration.

Just let the user fill in some fields, submit it to the server and if there are any errors notify them and let the user start over again. Is that a good approach? The answer is no, you don't want users to get frustrated waiting for a server round trip to get some form validation result.

Fonk is framework extension, and can be easily plugged into many libraries / frameworks, in this documentation you will find integrations with:

Add new plugin Recaptcha3Token that sends the reCaptcha v3 token to the back-end when the form is valid

that a better and cleaner approach would be to use computed properties and a validation library that is decoupled for the UI (like hapi/joi).

Form validation is hard. That's why there are so many different form handling libraries for the popular web frameworks. It's usually not something that is built-it, because everyone has a different need and there is no one-fit-all solution.

This style of validation most closely follows WordPress’ whitelist philosophy: only allow the user to input what you’re expecting.

Validate Forms

This rule has a few exceptions: It’s helpful to validate inline as the user is typing when creating a password (to check whether the password meets complexity requirements), when creating a user name (to check whether a name is available) and when typing a message with a character limit.

Ideally, inline validation messages should appear around 500 to 1000 milliseconds after the user has stopped typing or after they’ve moved to the next field.