Partial sum array

Creates an array of partial sums.

• Use Array.prototype.reduce(), initialized with an empty array accumulator to iterate over nums.
• Use Array.prototype.slice() to get the previous partial sum or 0 and add the current element to it.
• Use the spread operator (...) to add the new partial sum to the accumulator array containing the previous sums.

const accumulate = (...nums) =>
  nums.reduce((acc, n) => [...acc, n + (acc.slice(-1)[0] || 0)], []);

accumulate(1, 2, 3, 4); // [1, 3, 6, 10]
accumulate(...[1, 2, 3, 4]); // [1, 3, 6, 10]