how much have these type coercion issues actually affected us in practice? by using json and various frameworks i think our js code is pretty disciplined, and we aren't often comparing variables where we don't know what types are involved. on the other hand, when i tried to be a good js citizen and use '===', i immediately got bit by the difference between 'null' and 'undefined'. how often do we care about the difference between those two, and why should i use an operator that forces me to?