I would use the j Query validation plugin for a few reasons. You need to display the error, handle erasing it when it is valid, displaying how many errors total perhaps?
There are lots of things it can handle for you, no need to re-invent the wheel.
If you want to allow any kind of letters (not only A-Z) you're looking for the letternumeric validator.
Validate qty of checkboxes in a group (same name) have been checked, using min, max or range.
This is not intended to teach you everything there is to know.
Whilst many tags can be 'on' at any one time, under no circumstances should tags overlap.
The sixth installment in the series covers posting data with reactive forms and implementing custom validation in Angular. Let's add the API endpoints our app's administrator needs in order to create, update, and delete events.
In order to add a new event in our RSVP app, we'll create a new // server/...
Even though this plugin has a wide range of validation functions it's designed to require as little network traffic as possible.