# Create an array of cumulative sum

Replace each number with the running total up to it.

Canonical: https://1loc.dev/array/create-an-array-of-cumulative-sum/
Version: 1.0.0
Runtime: JavaScript · Node.js 22 / modern browsers
Verification: Local fixtures; no external services
Updated: 2026-10-28

## Implementation

```javascript
function accumulate(values) { let total = 0; return values.map(value => (total += value)); }
```

## Input

```json
[
  1,
  2,
  3,
  4
]
```

## Expected output

```json
[
  1,
  3,
  6,
  10
]
```

## Edge case

Input:
```json
[]
```
Output:
```json
[]
```

## Limits

- Floating-point totals can drift; sum integer minor units for money.

The lab validates types and size before calling this function. Add equivalent validation at your own trust boundary.

## Source and license

Original: https://github.com/phuocng/1loc/blob/14b481cf60dff1620ab1bb99a43b1f68068cdd9b/contents/create-an-array-of-cumulative-sum.mdx
Author: Nguyen Huu Phuoc and original contributors
Contributors: See original repository history
Source commit: 14b481cf60dff1620ab1bb99a43b1f68068cdd9b
Copyright (c) 2020 phuoc-ng
License: MIT — https://1loc.dev/licenses/
Maintainer: Oveyon
Modifications: Uses a running total instead of the closure-returning-closure variant. Original MDX retained as inert source evidence.