Along these lines, this is why I love hot-loading code. For example, there's react-hot-loader [0] (which was actually superseded already by react-transform [1]). This enables you to iterate much more quickly while you're building an interface. Along that same line, the same guy created redux and redux-devtools [2], which also enables you to iterate quickly on application code.
I've been using hotloading css, react and redux for the past few months and it's an amazing experience. It enables you to iterate quickly and see changes immediately. (Admittedly, as a project grows, there's a small delay between saving and seeing the change. I'm not sure if it's avoidable or not... But it's still much faster than having to do a full-page reload.)
[0] https://gaearon.github.io/react-hot-loader/