What is the time complexity of sum(1)(2)(3)..(n)?
O(n) where n is the number of chained calls. Each call creates a new function and closure. The space complexity is also O(n) due to the call stack (unless tail-call optimization is available, which it is not in most JS engines).
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More FAQs in How the sum(1)(2)(3) Function Uses Closures
Each call to sum(a) returns a function that closes over a. When called with b, it returns sum(a + b), creating a new closure with the accumulated total. The closure keeps the running sum alive between calls.
Yes. Each sum(a) call creates a new function with a new closure over a. The previous closure is replaced, but the accumulated value (a + b) is passed forward to the new sum call.
b is undefined. The function checks if (b !== undefined), which is false. It returns a (the accumulated sum). This is how the chain terminates and the result is retrieved.
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