A big challenge in writing web applications today is the intense pressure to go for the short term win: you quickly pull something together that looks good, launch, and move on. But the risk is that now you're locked in — making major changes over the lifetime of the code base requires radical surgery, or sometimes just starting over. Is it possible to meet your deadlines and get long term maintenance and reuse?Fortunately, modern JavaScript libraries offer some excellent patterns that can help you safely extend & reuse components for months and years to come — without over-engineering or sacrificing much development speed. The key is to build upon a solid foundation that gives you lots of flexibility down the road. In this interactive webcast presented by Evan Goer, author of YUI 3 Cookbook, we'll walk through some specific examples from the YUI Library that cleanly separate concerns, and then show how that pays off: first by radically altering a component's functionality without affecting its core plumbing, and then neatly packaging up that change as a plugin, as a "class-like" extension, and as a mixin.