get-reverse-iterating-array

get-reverse-iterating-array

A function returning an array whose iteration direction is reversed without affecting the original array or affecting the iteration direction of any other arrays.

By default, the iteration protocols are defined to iterate on an iterable object’s elements according to their insertion order.

The function getReverseIteratingArray returns a new Proxy object with the array being its target. The array’s [Symbol.iterator] property is trapped in order to define custom iteration behaviour. This has the advantage of not changing the implementation of Array.prototype[Symbol.iterator] directly which would cause the iteration direction of all arrays to be reversed. Using a proxy also avoids unnecessarily copying an array for reverse iteration like Array.prototype.reverse() would.

If you require to iterate over an array in both forwards and backwards direction, have a look at ReverseIterableArray.

Links:

• npmjs.com/package/get-reverse-iterating-array
• github.com/kleinfreund/get-reverse-iterating-array

See also:

• ReverseIterableArray: reverse-iterable-array
• ReverseIterableMap: reverse-iterable-map
• ReverseIterableSet: reverse-iterable-set

Table of contents

• Installation
• Usage
• Examples
• Tests
• Documentation

Installation

npm install get-reverse-iterating-array

Usage

import getReverseIteratingArray from 'get-reverse-iterating-array';

const array = getReverseIteratingArray([1, 2, 3]);

Examples

For some live usage examples, clone the repository and run the following:

npm install
npm run build
npm start

Then, open localhost:8080/examples in a browser.

Tests

In order to run the tests, clone the repository and run the following:

npm install
npm test

Documentation

Create a reverse-iterating array by passing any array to getReverseIteratingArray.

const reverseIteratingArray = getReverseIteratingArray([5, 4, 1, 2, 3]);

The returned object will behave like a regular built-in array with the exception of all cases involving the iteration protocols. The behaviour of the following concepts will be changed when used together with a reverse-iterating array:

• for..of statement

  for (const element of reverseIteratingArray) {
    console.log(element)
  }
  //> 3
  //> 2
  //> 1
  //> 4
  //> 5
  

• spread syntax

  [...reverseIteratingArray];
  //> [ 3, 2, 1, 4, 5 ]
  

• Array.from() method

  Array.from(reverseIteratingArray);
  //> [ 3, 2, 1, 4, 5 ]
  

• destructuring assignment

  const [a, b, c, d, e] = reverseIteratingArray
  //> a = 3, b = 2, c = 1, d = 4, e = 5