The answer
Use rest parameters: function sum(...args) { const total = args.reduce((a, b) => a + b, 0); return function(b) { if (b !== undefined) return sum(total + b); return total; }; }.
sum(1)(2)(3) Variations and Follow-Up Questions
How do you support sum(1, 2)(3) with multiple arguments?
More FAQs in sum(1)(2)(3) Variations and Follow-Up Questions
function sum(n) { const fn = m => sum(n + m); fn.toString = () => n; return fn; }. When JavaScript needs a primitive (like +0 or console.log), it calls toString and returns the accumulated sum.
How would you support multiple arguments (rest params), add other operations (multiply, subtract), make it a generic curry function, and what is the time/space complexity.
Yes. The chain can continue indefinitely: sum(1)(2)(3)(4)(5)...(n). It only terminates when you call with no argument (or when JavaScript calls toString for type coercion). Each call creates a new function.
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