This particular one is one of the oldest j Query plugins (started in July 2006) and has proved itself in projects all around the world.
That behaviour can be irritating when clicking through demos of the validation plugin – it is designed for an unobtrusive user experience, annoying the user as little as possible with unnecessary error messages.
So when you try out other demos, try to react like one of your users would, and see if the behaviour is better then.
If not, please let me know about any ideas you may have for improvements! Throughout the documentation, two terms are used very often, so it's important that you know their meaning in the context of the validation plugin: The validate method returns a Validator object that has a few public methods that you can use to trigger validation programmatically or change the contents of the form.
"But doesn't j Query make it easy to write your own validation plugin?
" Sure, but there are still a lot of subtleties to take care of: You need a standard library of validation methods (such as emails, URLs, credit card numbers).
You need to place error messages in the DOM and show and hide them when appropriate.
You want to react to more than just a submit event, like keyup and blur.
You may need different ways to specify validation rules according to the server-side enviroment you are using on different projects.
And after all, you don't want to reinvent the wheel, do you?