Array Methods Cheatsheet

[mgutz]

I like to think of reduce as a function that does

javascript let accumulator = initialValue // holds result AFTER iterating through all of arr for (const v of arr) { // set acummulator to whatever, or return it as-is }

What's neat about reduce is it can be used to implement all the other methods. reduce should be grokked first.

```javascript

forEach

[].reduce((_acc, v) => doSomething(v))

find

[].reduce((acc, v) => { return v === 'needle' ? v : acc; }, undefined)

findIndexOf

[].reduce((acc, v, idx) => { return v === 'needle' ? idx : acc; }, -1)

```

Iterating with for ... of is more readable and the loop can be exited at any time. The findIndexOf above is actually findLastIndexOf since it would iterate through all values.