get-nested-array-element-by-position

Project website at oscbco-libraries.gitlab.io/get-nested-array-element-by-position/

This small library allows for traversing a structure of nested arrays as a single one-dimensional array. Making it possible to use a single for loop to iterate through all the nested array nodes

Nodes are returned by their position in the nested structure.

Nodes in the current array will be returned first, however if a node has a "child array" then nodes in the "child array" are returned before continuing with the current array. This is true for their children as well.

Required properties for these array structures:

An object with these 2 properties:

value: This is the payload of the node.

child: Reference to the child array, or if it doesn't have one then it MUST be null

Installation:

  npm install --save @oscbco/get-nested-array-element-by-position

You can import it like this:

  let getNestedArrayElementByPosition = require('@oscbco/get-nested-array-element-by-position');

For example, the following code:

  const getNestedArrayElementByPosition = require('@oscbco/get-nested-array-element-by-position');

  const collection = [
    {
      value: '/public',
      child: [
        {
          value: '/public/js',
          child: [
            {
              value: '/public/js/index.js',
              child: null
            }
          ]
        }
      ]
    },
    {
      value: '/public/images',
      child: [
        {
          value: '/public/images/logo.png',
          child: null
        },
        {
          value: '/public/images/header.png',
          child: null
        },
        {
          value: '/public/images/background.png',
          child: null
        }
      ]
    },
    {
      value: '/source',
      child: [
        {
          value: '/source/index.js',
          child: null
        }
      ]
    }
  ];

  let counter = 0;
  let node = null;
  let concatenatedNodes = '';
  do {
    node = getNestedArrayElementByPosition.findNode({collection, requestedIndex: counter});
    concatenatedNodes += node.value ? node.value + '\n' : '';
    counter++;
  } while (node.keypath !== undefined);
  console.log(concatenatedNodes);

  console.log("Example: Node at position 6\n", JSON.stringify(getNestedArrayElementByPosition.findNode({collection, requestedIndex: 6}), null, 2));

  console.log("Example: Node at a nonexistent position\n", JSON.stringify(getNestedArrayElementByPosition.findNode({collection, requestedIndex: 9}), null, 2));

Results in:

/public
/public/js
/public/js/index.js
/public/images
/public/images/logo.png
/public/images/header.png
/public/images/background.png
/source
/source/index.js

Example: Node at position 6
{
  "value": "/public/images/background.png",
  "count": 6,
  "keypath": [
    1,
    2
  ]
}
Example: Node at a nonexistent position
{}

findNode returns the value property of the node as well as the count and keypath.

count and keypath are used by the library to speed up subsequent lookups because we don't have to start counting from zero, instead we use the last known count and keypath and start from there.

If a node at a given position does not exist, then findNode returns:

  {
    value: undefined,
    count: undefined,
    keypath: undefined
  }

ToDo:

• Wrap the array structure in a class and add CRUD methods
• A method to count all elements

Development

If you want more info on how this project is structured and how this helps with development, testing, building the documentation and its own static website visit: http://oscbco-boilerplate.gitlab.io/webpack-npm-library-boilerplate/