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30-seconds-of-code/snippets/reduceSuccessive.md
Mathias Bynens f2e5e26af3 Avoid confusing prototype methods for static methods
Correct: `Array.from()` (it’s a static method)
Incorrect: `Array.join()` (doesn’t exist; it’s a prototype method)

This patch uses the common `#` syntax to denote `.prototype.`.
2018-09-28 15:44:12 -04:00

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### reduceSuccessive
Applies a function against an accumulator and each element in the array (from left to right), returning an array of successively reduced values.
Use `Array.prototype.reduce()` to apply the given function to the given array, storing each new result.
```js
const reduceSuccessive = (arr, fn, acc) =>
arr.reduce((res, val, i, arr) => (res.push(fn(res.slice(-1)[0], val, i, arr)), res), [acc]);
```
```js
reduceSuccessive([1, 2, 3, 4, 5, 6], (acc, val) => acc + val, 0); // [0, 1, 3, 6, 10, 15, 21]
```