20 lines
393 B
Markdown
20 lines
393 B
Markdown
---
|
|
title: head
|
|
tags: array,beginner
|
|
---
|
|
|
|
Returns the head of a list.
|
|
|
|
Check if `arr` is truthy and has a `length` property, use `arr[0]` if possible to return the first element, otherwise return `undefined`.
|
|
|
|
```js
|
|
const head = arr => (arr && arr.length ? arr[0] : undefined);
|
|
```
|
|
|
|
```js
|
|
head([1, 2, 3]); // 1
|
|
head([]); // undefined
|
|
head(null); // undefined
|
|
head(undefined); // undefined
|
|
```
|