Ah, I see what you mean. Thanks for the explanation. This is just my opinion but doing that seems to be very dangerous. You're probably fine for small function

Ah, I see what you mean. Thanks for the explanation. This is just my opinion but doing that seems to be very dangerous. You're probably fine for small functions with single-developers, but once you get complex and have multiple people working on the code it seems easy for one dev to confuse another. If you insist on that pattern (lets call it the local variable method) you can define vars such as var localA = a var localB = b at the top of the function and work on it there. Personally I prefer function arguments to be immutable, so that any time you call them you know what you're working on is what the function was given. Forcing you to declare a local var makes the code much more explicit and easy for another human to reason about what you're doing, whereas they could very easily miss an "a=something else".