I had an opportunity to work also with non-Ext frameworks while I was integrating wonderful Bryntum Scheduler and Gantt to Angular, React and while doing so I had to learn about the other frameworks. I already have a lot of experiences with ExtJS and I have written many large production-grade applications in this framework.
Although Sencha Cmd is a very useful tool for application scaffolding, creating view, controllers and models, sometimes it is faster to use a single-file app. It is especially useful for fast testing, prototyping or concept proof. Read how to do it.