Unobtrusive JavaScript" is a general approach to the use of JavaScript in web pages. Though the term is not formally defined, its basic principles are generally understood to include:
Separation of functionality (the "behavior layer") from a Web page's structure/content and presentation
Best practices to avoid the problems of traditional JavaScript programming (such as browser inconsistencies and lack of scalability)
Progressive enhancement to support user agents that may not support advanced JavaScript functionality[2]
