A reverse-iterable array implementation based on the built-in Array object
npm install reverse-iterable-arrayThe ReverseIterableArray object is a reverse-iterable array implementation based on the built-in Array object.
Links:
- npmjs.com/package/reverse-iterable-array
- on BundlePhobia
- github.com/kleinfreund/reverse-iterable-array
See also:
- ReverseIterableMap: reverse-iterable-map
- ReverseIterableSet: reverse-iterable-set
- Installation
- Usage
- Examples
- Tests
- Documentation
- Constructor
- [[Symbol.toStringTag]](#symboltostringtag)
- entries()
- forEachReverse()
- iteratorFor()
- keys()
- reverseIterator()
- values()
- [[Symbol.iterator]()](#symboliterator)
``sh`
npm install reverse-iterable-array
`js
import ReverseIterableArray from 'reverse-iterable-array';
const array = new ReverseIterableArray();
`
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 in a browser.
In order to run the tests, clone the repository and run the following:
`sh`
npm install
npm test
A ReverseIterableArray object iterates its elements in insertion or reverse-insertion order — a for...of loop returns the array’s elements for each iteration.
#### Syntax
`
new ReverseIterableArray([iterable])
Parameters:
- iterable: An iterable 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> ]
The ReverseIterableArray[@@toStringTag] property has an initial value of “ReverseIterableArray”.
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
`
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
`
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
`
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
`
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 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
`
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
`
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
`
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]
``