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use instanceof to determine if arg is an array

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Dym Sohin
2020-07-08 07:50:51 +02:00
committed by GitHub
parent 1a1e78007a
commit 1779093724
1 changed files with 3 additions and 2 deletions
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snippets/last.md
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@ -5,10 +5,11 @@ tags: array,beginner
Returns the last element in an array.
Check if `arr` is truthy and has a `length` property, use `arr.length - 1` to compute the index of the last element of the given array and return it, otherwise return `undefined`.
Check if `arr` is an instance of an `Array`, use `arr.length - 1` to compute the index of the last element of the given array and return it, otherwise return `undefined`.
```js
const last = arr => (arr && arr.length ? arr[arr.length - 1] : undefined);
const last = arr =>
(arr instanceof Array ? arr[arr.length - 1] : undefined);
```
```js