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https://github.com/kleinfreund/reverse-iterable-array
A reverse-iterable array implementation based on the built-in Array object.
https://github.com/kleinfreund/reverse-iterable-array
array iterable iterator reverse-iterable
Last synced: about 2 months ago
JSON representation
A reverse-iterable array implementation based on the built-in Array object.
- Host: GitHub
- URL: https://github.com/kleinfreund/reverse-iterable-array
- Owner: kleinfreund
- License: mit
- Created: 2018-08-09T17:58:47.000Z (over 6 years ago)
- Default Branch: main
- Last Pushed: 2024-10-20T18:58:16.000Z (2 months ago)
- Last Synced: 2024-10-21T02:11:29.500Z (2 months ago)
- Topics: array, iterable, iterator, reverse-iterable
- Language: JavaScript
- Homepage: https://www.npmjs.com/package/reverse-iterable-array
- Size: 784 KB
- Stars: 3
- Watchers: 3
- Forks: 0
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE.txt
Awesome Lists containing this project
README
# reverse-iterable-array
The `ReverseIterableArray` object is a reverse-iterable array implementation based on the built-in [Array](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array) object.
Links:
- [**npmjs.com**/package/reverse-iterable-array](https://www.npmjs.com/package/reverse-iterable-array)
- [on BundlePhobia](https://bundlephobia.com/result?p=reverse-iterable-array)
- [**github.com**/kleinfreund/reverse-iterable-array](https://github.com/kleinfreund/reverse-iterable-array)
See also:
- `ReverseIterableMap`: [reverse-iterable-map](https://www.npmjs.com/package/reverse-iterable-map)
- `ReverseIterableSet`: [reverse-iterable-set](https://www.npmjs.com/package/reverse-iterable-set)
## Table of Contents
- [Installation](#installation)
- [Usage](#usage)
- [Examples](#examples)
- [Tests](#tests)
- [Documentation](#documentation)
- [Constructor](#constructor)
- [`[Symbol.toStringTag]`](#symboltostringtag)
- [`entries()`](#entries)
- [`forEachReverse()`](#foreachreverse)
- [`iteratorFor()`](#iteratorfor)
- [`keys()`](#keys)
- [`reverseIterator()`](#reverseiterator)
- [`values()`](#values)
- [`[Symbol.iterator]()`](#symboliterator)
## Installation
```sh
npm install reverse-iterable-array
```
## Usage
```js
import ReverseIterableArray from 'reverse-iterable-array';
const array = new ReverseIterableArray();
```
## Examples
For some live usage examples, clone the repository and run the following:
```sh
npm install
npm run build
npm start
```
Then, open [localhost:8080/examples](http://127.0.0.1:8080/examples) in a browser.
## Tests
In order to run the tests, clone the repository and run the following:
```sh
npm install
npm test
```
## Documentation
A `ReverseIterableArray` object iterates its elements in insertion or reverse-insertion order — a [`for...of`](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...of) loop returns the array’s elements for each iteration.
### Constructor
#### Syntax
```
new ReverseIterableArray([iterable])
```
**Parameters**:
- `iterable`: An [iterable](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Iteration_protocols#The_iterable_protocol) object.
#### Usage
- Without arguments
```js
const array = new ReverseIterableArray();
//> Array []
```
- With multiple elements
```js
const array = new ReverseIterableArray(1, 2, 3);
//> Array(3) [ 1, 2, 3 ]
```
- With a single length argument
```js
const array = new ReverseIterableArray(7);
//> Array(7) [ <7 empty slots> ]
```
### `[Symbol.toStringTag]`
The `ReverseIterableArray[@@toStringTag]` property has an initial value of “ReverseIterableArray”.
### `entries()`
Returns an iterator containing the `[index, element]` pairs for each element in the `ReverseIterableArray` object in insertion order.
An iterator containing the same pairs in reverse-insertion order can be obtained with `entries().reverseIterator()`.
#### Syntax
```
array.entries();
```
**Return value**:
A new `ReverseIterableArray` iterator object.
#### Usage
```js
const array = new ReverseIterableArray(1, 2, 4);
const iterator = array.entries();
iterator.next().value;
//> [0, 1]
iterator.next().value;
//> [1, 2]
iterator.next().value;
//> [2, 4]
iterator.next().value;
//> undefined
```
### `forEachReverse()`
The `forEachReverse()` method executes a provided function once per each `[index, element]` pair in the `ReverseIterableArray` object, in reverse-insertion order.
#### Syntax
```
array.forEachReverse(callback[, thisArg]);
```
**Parameters**:
- **callback**: Function to execute for each element.
- **thisArg**: Value to use as `this` when executing `callback`.
#### Usage
```js
const array = new ReverseIterableArray('a', 'b', 'c');
array.forEachReverse(value => {
console.log(value);
});
//> c
//> b
//> a
array.forEachReverse(function (value, key, arrayReference) {
console.log(key, value, arrayReference.size);
});
//> 2 c 3
//> 1 b 3
//> 0 a 3
```
### `iteratorFor()`
Returns an iterator containing the `[index, element]` pairs for each element in the `ReverseIterableArray` object in insertion order **starting with the pair specified by the `index` parameter**.
This allows starting iteration at a specific element in the array.
An iterator containing the same pairs in reverse-insertion order can be obtained with `iteratorFor(index).reverseIterator()`.
#### Syntax
```
array.iteratorFor(index);
```
**Parameters**:
- **index**: Required. The index of the element to start iterating from.
**Return value**:
A new `ReverseIterableArray` iterator object.
#### Usage
```js
const array = new ReverseIterableArray('a', 'b', 'c');
// Iterator, starting at the element with key 1.
const iterator = array.iteratorFor(1);
iterator.next().value;
//> [1, 'b']
iterator.next().value;
//> [2, 'c']
iterator.next().value;
//> undefined
// Reverse-iterator, starting at the element with key 1.
const reverseIterator = array.iteratorFor(1).reverseIterator();
reverseIterator.next().value;
//> [1, 'c']
reverseIterator.next().value;
//> [0, 'a']
reverseIterator.next().value;
//> undefined
```
### `keys()`
Returns an iterator containing the indices for each element in the `ReverseIterableArray` object in insertion order.
An iterator containing the same indices in reverse-insertion order can be obtained with `keys().reverseIterator()`.
#### Syntax
```
array.keys();
```
**Return value**:
A new `ReverseIterableArray` iterator object.
#### Usage
```js
const array = new ReverseIterableArray(1, 2, 4);
const iterator = array.keys();
iterator.next().value;
//> 0
iterator.next().value;
//> 1
iterator.next().value;
//> 2
iterator.next().value;
//> undefined
```
### `reverseIterator()`
In theory, following the semantics of `[Symbol.iterator]()`, this should be `[Symbol.reverseIterator]()`. However, as a developer, I cannot define a well-known symbol myself and make use of it. In the future, the a proposal like [The ReverseIterable Interface, by Lee Byron](https://github.com/leebyron/ecmascript-reverse-iterable) might make it’s way into the specification. For the time being, the `reverseIterator()` function serves the same purpose.
#### Syntax
```
array.reverseIterator();
```
**Return value**:
The array **reverse-iterator** function, which is the `values().reverseIterator()` function by default.
#### Usage
```js
const array = new ReverseIterableArray(1, 2, 4);
const iterator = array.reverseIterator();
iterator.next().value;
//> [2, 4]
iterator.next().value;
//> [1, 2]
iterator.next().value;
//> [0, 1]
iterator.next().value;
//> undefined
```
### `values()`
Returns an iterator containing the elements in the `ReverseIterableArray` object in insertion order.
An iterator containing the same elements in reverse-insertion order can be obtained with `values().reverseIterator()`.
#### Syntax
```
array.values();
```
**Return value**:
A new `ReverseIterableArray` iterator object.
#### Usage
```js
const array = new ReverseIterableArray(1, 2, 4);
const iterator = array.values();
iterator.next().value;
//> 1
iterator.next().value;
//> 2
iterator.next().value;
//> 4
iterator.next().value;
//> undefined
```
### `[Symbol.iterator]()`
Returns the array iterator function. By default, this is the `values()` function.
#### Syntax
```
array[Symbol.iterator]();
```
**Return value**:
The array **iterator** function, which is the `entries()` function by default.
#### Usage
```js
const array = new ReverseIterableArray(1, 2, 4);
const iterator = array[Symbol.iterator]();
iterator.next().value;
//> 1
iterator.next().value;
//> 2
iterator.next().value;
//> 4
iterator.next().value;
//> undefined
```
### `[Symbol.toStringTag]()`
The well-known symbol `Symbol.toStringTag` is accessed internally when callig `Object.prototype.toString()`.
#### Usage
```js
const array = new ReverseIterableArray();
Object.prototype.toString.call(array)
//> [object ReverseIterableArray]
```