No-Library (pure JS), HTML, CSS, JavaScript
http://angularjs.org/
Here is a basic example of using JQuery keypress, keyup to run against a URL validation function. No plugin is needed!
Mootools 1.4.5, HTML, CSS, JavaScript
Mootools 1.4.2, HTML, CSS, JavaScript
Mootools 1.4.3 (compat), HTML, CSS, JavaScript