console.log('sum(1)(2)(3)(4)..( n)()'); // Solution 1: let sum = function (a) { return function (b) { if (b) { return sum(a + b); } return a; } } let result = sum(1)(2)(3)(4)(5)(); console.log(result); // 15 // Solution 2: let sum = (a) => (b) => (b) ? sum(a+b) : a; let result = sum(1)(2)(3)(4)(5)(); console.log(result); // 15