Is sum(1)(2)(3) an Amazon interview question?
Yes. Amazon asks candidates to implement a curried sum function that chains indefinitely. It tests understanding of currying, closures, function chaining, and JavaScript type coercion (if using toString).
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More FAQs in Implement sum(1)(2)(3)(4)..(n) in JavaScript
function sum(a) { return function(b) { if (b !== undefined) return sum(a + b); return a; }; }. Each call returns a function that accumulates. Call with no argument to get the result: sum(1)(2)(3)().
Two approaches: (1) call with no argument: sum(1)(2)(3)() - check if b !== undefined. (2) toString override: sum(1)(2)(3) + 0 - JavaScript calls toString when arithmetic is performed.
Currying and closures. Each call returns a function that closes over the accumulated sum. Without closures, the inner function would not have access to the previous arguments.
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