Using jQuery to Create the Virtual iPhone & Virtual iPad
While it may be educational and fun to write all the JavaScript code for the Virtual iPhone & Virtual iPad from scratch, it would be extremely time consuming. An article by Oliver Mezquita Prieto really sums up the reasons to use a JavaScript framework:
1. Saves you time. Even if you really love programming in Javascript, you will save a bunch of time doing your work with one these frameworks.
2. Has much of your work already done. Don’t reinvent the wheel. Don’t waste time in doing something it has already been done and tested and re-tested by thousands of users.
3. Makes you use less code. With less code you get a smaller file size, better maintenance and less development time.
4. Makes your code more readable. Which also aids in better maintenance and less development time.
5. Makes your web application execute faster. These frameworks are really fast in performing their tasks and most of them have been optimized for really fast execution.
6. Makes your web application run in most modern browsers. If you dealt with Javascript a bit, you’ll have realized how different browsers have different ways of the doing the same exact stuff. Handcrafted cross-browser development can get annoying and irritating. These frameworks have already taken care of that and will just work in most browsers.
Fortunately, there are many JavaScript libraries available to streamline the coding process. There is a comparison list that I used to try and decide which framework would be best. I started to use Yahoo! UI Library but I quickly found the code to be cumbersome and not intuitive. So I went back and looked at a few others. In the end, I decided to go with jQuery for the reason mentioned on their website:

jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript.
via jQuery