Having worked with both the ArcGIS Silverlight and Javascript APIs I have to say Javascript has been much more fun. There is just something about working on the front end of a web map and being able to have it do so many amazing things. Here are my top five reasons I enjoy working with this API.
1. Your maps are device independent. Unlike the Flex and Silverlight APIs, Javascript and HTML5 can be viewed on almost any device. The obvious advantage here is that you can reach more people with your spatial data. Of course having the ability to code for multiple devices means having to customize your code for different screen sizes which can turn into a lot of work. Check out this post from the Treehouse Blog for a great primer on responsive web design.
2. Plenty of code samples and live examples. Code samples are a great way to get your own map up and running quickly without having to figure everything out first. While the samples are not perfect they are a good way to discover map functionality that you might want to incorporate.
3. Support for a ton of layer and data formats. From GeoRSS and GeoJSON to KML and shapefile, this API pretty much covers it.
4. Well written API reference documentation. If you are going to use an API (any API) you want to be able to understand it so you can use it effectively. Good documentation is critical for this. The Esri JS API is (in my own humble opinion) extremely easy to read and understand. Each class has all the information you need to use it without having to decode any meanings. Furthermore, there are links from each class to samples that use it.
5. Editing tools for online editing of SDE data. Let’s be honest, online editing through a web browser is not a great idea if you are trying to build accurate data. However, there is definitely a place for it. If you are trying to outline an area inhabited by a herd of elk or mark an area of weed infestation, browser editing is probably fine. It is great just to be able to have this ability so more diverse mapping applications can be developed.
Wow, this list was a lot harder to write than 5 Things I Hate About the ESRI Javascript API. One reason is that there are other APIs out there that do a lot of what the ESRI API does (yes I am thinking about OpenLayers). Another reason is that as I write I think about things I would like ESRI to do better or differently. Oh well, you can’t have everything. Let me know what your thoughts are on the ESRI Javascript API – good or bad.