Although the Joomla! Project has decided to make jQuery the JavaScript library of choice going forward with Joomla 3, MooTools will continue to be included in the base install of Joomla. This means that developers will have a choice in which library they would like to use; however, there is a strong push to move toward jQuery as a whole.
JavaScript libraries such as MooTools provide reusable code for often needed effects and behaviors, such as accordions, sliders, progress bars, form validation and alerts.
