The jQuery library provides developers with a common code base to reuse that has been optimized for the web and tested for security and cross-browser compatibility. The modular nature of jQuery means that developers can also create their own versions of the library based on what effects and behaviors they are using in any given website project, leaving out code that will never be used.

JavaScript libraries such as jQuery and MooTools provide easier ways of coding things like accordions, slide shows, drop downs and other form elements into websites. They also provide functions like form validation for greater website security.