"But doesn't j Query make it easy to write your own validation plugin?
In all cases, the form is called That's checking the value's equality with a null String (two single quotes with nothing between them).
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.
There is also an article discussing how this plugin fits the bill of the should-be validation solution. Have a look at this example: A single line of j Query to select the form and apply the validation plugin, plus a few annotations on each element to specify the validation rules.
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.