If you compare try to understand actually JavaScript has the most accessible (for normal mortal) on the state of the system. IPython you have to type and sort

If you compare try to understand actually JavaScript has the most accessible (for normal mortal) on the state of the system. IPython you have to type and sort of print. Python on code might help as you can checkpoint and get some state during that checkpoint. If there is no problem I am not sure lisp give that much (for our mortal). Obviously when problem occur in unexpected place and suddenly the availability of the stack is great. And that is lisp winning. Not sure for general understanding as usually you have a case in mind and want to trace the state. In that case still think JavaScript, Python with code, iPython for document still ok.