mirror of
https://github.com/alrayyes/wiki.git
synced 2024-11-25 04:56:23 +00:00
108 lines
2.2 KiB
Markdown
108 lines
2.2 KiB
Markdown
---
|
|
date: 20201009
|
|
id: c76b3766-a1ed-43f9-bdb6-4076e6bb5b7a
|
|
title: JavaScript Array Methods
|
|
---
|
|
|
|
# ES6
|
|
|
|
## Static Array methods
|
|
|
|
### Array.from()
|
|
|
|
``` javascript
|
|
const arr2 = Array.from(arguments); // ES6
|
|
```
|
|
|
|
If a value is [iterable](20201014092625-javascript_iterables) (as all
|
|
Array-like DOM data structure are by now), you can also use the
|
|
[spread](20201014094144-spread) operator (…) to convert it to an
|
|
[Array](20200826201029-arrays):
|
|
|
|
``` javascript
|
|
const arr1 = [...'abc'];
|
|
// ['a', 'b', 'c']
|
|
const arr2 = [...new Set().add('a').add('b')];
|
|
// ['a', 'b']
|
|
```
|
|
|
|
### Array.of()
|
|
|
|
This returns an array of the passed parameters
|
|
|
|
``` javascript
|
|
console.log(Array.of(1, 2, 3, 4)) // [1, 2, 3, 4]
|
|
```
|
|
|
|
## Array.prototype methods
|
|
|
|
### Array.prototype.fill()
|
|
|
|
``` javascript
|
|
const arr2 = new Array(2).fill(undefined);
|
|
// [undefined, undefined]
|
|
```
|
|
|
|
### Array.prototype.copyWithin()
|
|
|
|
The method signature is:
|
|
|
|
``` typescript
|
|
Array.prototype.copyWithin(target : number,
|
|
start : number, end = this.length) : This
|
|
```
|
|
|
|
It copies the elements whose indices are in the range \[start,end) to
|
|
index target and subsequent indices. If the two index ranges overlap,
|
|
care is taken that all source elements are copied before they are
|
|
overwritten. I am confused as to how this is in any way useful.
|
|
|
|
``` javascript
|
|
const arr = [0,1,2,3];
|
|
console.log(arr.copyWithin(2, 0, 2)) // [0, 1, 0, 1]
|
|
```
|
|
|
|
### Searching for elements
|
|
|
|
1. Array.prototype.findIndex()
|
|
|
|
``` javascript
|
|
console.log([6, -6, 8].findIndex(x => x < 0)) // 1
|
|
```
|
|
|
|
2. Array.prototype.find()
|
|
|
|
``` javascript
|
|
console.log([6, -6, 8].find(x => x < 0)) // -6
|
|
```
|
|
|
|
### Iteration
|
|
|
|
1. Array.prototype.entries()
|
|
|
|
``` javascript
|
|
console.log(Array.from(['a', 'b'].entries())) // [ [ 0, 'a' ], [ 1, 'b' ] ]
|
|
```
|
|
|
|
2. Array.prototype.values()
|
|
|
|
``` javascript
|
|
console.log(Array.from(['a', 'b'].values())) // ['a', 'b']
|
|
```
|
|
|
|
3. Array.prototype.keys()
|
|
|
|
``` javascript
|
|
console.log(Array.from(['a', 'b'].keys())) // [0, 1]
|
|
```
|
|
|
|
# ES2016
|
|
|
|
## Array.prototype.includes()
|
|
|
|
Tells you if array includes a certain element:
|
|
|
|
``` javascript
|
|
console.log(["a", "b", "c"].includes("a")); // true
|
|
console.log(["a", "b", "c"].includes("d")); // false
|
|
```
|