Let me preface this with the fact that I am a Flex dev who ventured into the HTML/JS/CSS stack during the "Flexodus". Cleary, ExtJS seemed to suit my fancy mor

Let me preface this with the fact that I am a Flex dev who ventured into the HTML/JS/CSS stack during the "Flexodus". Cleary, ExtJS seemed to suit my fancy more than the other libraries in the JS world. As far as why it doesn't have traction, I would attribute this to 2 things. The first being that the JS community isn't really into app development. What I mean by that, is when you look at JS, and you look at languages like Flex and Silverlight, you notice a massive disconnect in ideas. In the JS world, visual components are rarely if ever first class citizens, simple layout tasks are far more difficult than they need to be, and SPA paradigms are also second class citizens. After noticing this and poking around, you find out that the main JS community either doesn't want the solution to begin with, or they seem to be re-inventing the wheel. The second strike against ExtJS is the cost. I got a license for it a few years ago when I was delusional and thought I could use it to replace Flex. Dropping $1,000 on something when virtually every other tech out there is free is hard to choke down. Also, it seemed like a major step down for those of us coming from the Flex community. Like I said, with JS app paradigms seem like afterthoughts and each peculiarity wore me down further and further. For instance, if you have a button and you declare a listener function but misspell it, you don't get an error complaining that the listener doesn't exist, you get a blank white screen. Another issue was marshalling data into objects. Whenever I brought back a Classroom JSON representation, the Student objects in the students collection remained unmarshalled. I had to use ANOTHER store to get those to behave as objects. All of these "why on earth is this acceptable" moments led me to believe such features weren't really in demand in the JS community if not resented altogether.