30-seconds-of-code/snippets/accumulate.md

title, tags, expertise, author, firstSeen, lastUpdated

title	tags	expertise	author	firstSeen	lastUpdated
Partial sum array	math,array	intermediate	chalarangelo	2020-05-04T12:20:46+03:00	2022-01-30T13:10:13+02:00

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]