Update accumulate

snippets/accumulate.md

@@ -2,17 +2,18 @@
 title: accumulate
 tags: math,array,intermediate
 firstSeen: 2020-05-04T12:20:46+03:00
-lastUpdated: 2020-11-03T21:46:13+02:00
+lastUpdated: 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(-1)`, the spread operator (`...`) and the unary `+` operator to add each value to the accumulator array containing the previous sums.
+- 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.
 
 ```js
 const accumulate = (...nums) =>
-  nums.reduce((acc, n) => [...acc, n + +acc.slice(-1)], []);
+  nums.reduce((acc, n) => [...acc, n + (acc.slice(-1)[0] || 0)], []);
 ```
 
 ```js