1. Essential Dojo

Dojo is the premier JavaScript toolkit for use in Web pages. It gives you just about all the power you can squeeze out of JavaScript, providing powerful new controls (colorpickers, text box validation, menus, dialog boxes, calendars, and more).

Dojo also smoothes out the differences between browsers, eliminating all the annoying differences between browsers that JavaScript programmers have to deal with otherwise. You can use it in many different types of browsers without changing your code—that’s a major attraction of Dojo.