After learning alot about EXTJS, it makes sense to get familiar with jQuery. If you have 15 minutes, this is a good overview. Similarly, try this slide share too as it provides good explanations. As well, there is a jQuery fundamentals, an online book or jQuery in Action. As the first chapter says :
If you’ve spent any time at all trying to add dynamic functionality to your pages, you’ve found that you’re constantly following a pattern of selecting an element or group of elements and operating upon those elements in some fashion. You could be hiding or revealing the elements, adding a CSS class to them, animating them, or modifying their attributes.
To collect a group of elements, we use the simple syntax:
Then, jQuery provides methods (or sometimes known as commands or actions) that can act on the group of elements. Some of these actions when completed return the same set of elements that can then again be acted on (known as chaining).
jQuery. or $. is the notation for utility functions.