const accumulate = arr => arr.map((sum => value => sum += value)(0)); // Example accumulate([1, 2, 3, 4]); // [1, 3, 6, 10] // 1 = 1 // 1 + 2 = 3 // 1 + 2 + 3 = 6 // 1 + 2 + 3 + 4 = 10