Emergent Web Technologies Spring 2009 Class 4

Introduction

Just a little bit more for JavaScript basics this week. Specifically, Object Oriented JavaScript. JavaScript doesn't actually have "classes" per se, but it does have objects and objects can be copied in a way that's similar to the way that classes work in other languages.

Also covered this week: JSON with Padding or JSONP. JSONP is basically a hack to get around the fact that Ajax calls cannot be made across domains. Despite the fact that it's a hack, some sites make use of it for their JavaScript APIs, so it's a helpful trick to know. jQuery wraps up JSONP calls in a function that makes it easy to do.

Finally, I'm introducing the Google Maps API using the Google API Playground. The API playground is a nice way to try out Google's APIs without needing to configure things on your own.

In Class Activities

Activity 1

Build a word counter for textarea tags. This is an activity that demonstrates how you can use object oriented JavaScript to build reusable JavaScript components on your pages.

Adding a new wordcounter should be a simple as this:

   new WordCount(textareaNode);

You can copy the template here