textarea word count limiter

I need a generic javascript control that will allow me to count the words input into a text area and if XXX number of words are input, alert the user the max number of words allowed has been reached, and then disable any further input. I need to have multiple textareas on the form each with potentially a different word limit. These options need to be toggleable to on or off I need to display (as text not an input box), the total number of words allowed and have it dynamically count down. I need to pop an alert box when XXX words remain I need to pop an alert box when the limit is reached Input in to the textarea must stop at the limit unless the user removes some words.