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[guide] Updated Arrays Section

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- corrected paragraph 4.4 (conversion from iterable to array)
- added paragraph 4.5 (conversion from array-like to array)
This commit is contained in:
Mauro Zenoni
2018-07-03 11:51:37 +02:00
committed by Jordan Harband
parent fe8de59977
commit 5d1f4b9a49
1 changed files with 19 additions and 5 deletions
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README.md
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@@ -369,8 +369,9 @@ Other Style Guides
const itemsCopy = [...items];
```
<a name="arrays--from"></a><a name="4.4"></a>
- [4.4](#arrays--from) To convert an array-like object to an array, use spreads `...` instead of [`Array.from`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/from).
<a name="arrays--from">
<a name="arrays--from-iterable"></a><a name="4.4"></a>
- [4.4](#arrays--from-iterable) To convert an iterable object to an array, use spreads `...` instead of [`Array.from`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/from).
```javascript
const foo = document.querySelectorAll('.foo');
@@ -382,8 +383,21 @@ Other Style Guides
const nodes = [...foo];
```
<a name="arrays--from-array-like"></a>
- [4.5](#arrays--from-array-like) Use [`Array.from`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/from) for converting an array-like object to an array.
```javascript
const arrLike = { 0: 'foo', 1: 'bar', 2: 'baz', length: 3 };
// bad
const arr = Array.prototype.slice.call(arrLike);
// good
const arr = Array.from(arrLike);
```
<a name="arrays--mapping"></a>
- [4.5](#arrays--mapping) Use [Array.from](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/from) instead of spread `...` for mapping over iterables, because it avoids creating an intermediate array.
- [4.6](#arrays--mapping) Use [`Array.from`](https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Array/from) instead of spread `...` for mapping over iterables, because it avoids creating an intermediate array.
```javascript
// bad
@@ -394,7 +408,7 @@ Other Style Guides
```
<a name="arrays--callback-return"></a><a name="4.5"></a>
- [4.6](#arrays--callback-return) Use return statements in array method callbacks. It’s ok to omit the return if the function body consists of a single statement returning an expression without side effects, following [8.2](#arrows--implicit-return). eslint: [`array-callback-return`](https://eslint.org/docs/rules/array-callback-return)
- [4.7](#arrays--callback-return) Use return statements in array method callbacks. It’s ok to omit the return if the function body consists of a single statement returning an expression without side effects, following [8.2](#arrows--implicit-return). eslint: [`array-callback-return`](https://eslint.org/docs/rules/array-callback-return)
```javascript
// good
@@ -441,7 +455,7 @@ Other Style Guides
```
<a name="arrays--bracket-newline"></a>
- [4.7](#arrays--bracket-newline) Use line breaks after open and before close array brackets if an array has multiple lines
- [4.8](#arrays--bracket-newline) Use line breaks after open and before close array brackets if an array has multiple lines
```javascript
// bad