@codefeathers/infinity

∞

Infinity

Create infinite linked lists in JavaScript. Each item is linked to the next and previous item.

This can also be used as an n^th generator with a pure interface (see example).

Installation

Node:

npm install --save @codefeathers/infinity

In the browser:

<script src="https://unpkg.com/@codefeathers/infinity">

Usage

// Initialise a new InfiniteList using the constructor.
// `start` is any value.
// `next` is a pure function that accepts current
// (and optionally previous) value in the series

const infinity = new InfiniteList(<start:Number>, <next:Function>);

// Gets item at index
infinity.get(<index:Number>);

// Equivalent to the above! (Modern browsers and node only)
infinity[<index:Number>];

// Returns array of given number of InfiniteListItems from index 0
infinity.take(<number:Number>);

// Returns array of InfiniteListItems from index startIndex to endIndex
infinity.take(<startIndex:Number>, <endIndex:Number>);

// Get InfiniteListItem at next index. Optional number of indices to move ahead
infinity.get(<index:Number>).next(<number:Number>);

// Get InfiniteListItem at previous index. Optional number of indices to move backward
infinity.get(<index:Number>).previous(<number:Number>);

You can pass in any starting value. infinity cheerfully ignores what you pass in there. The next function gets current value and (optionally) previous value as arguments to find next value.

InfiniteList is iterable.

// (Modern browsers and node only)
for (let item of infinity) {
	// Remember to have an exit condition
	console.log(item);
}

Example

const InfiniteList = require('@codefeathers/infinity');
const { log } = console;

const next = (cur, prev) => cur + ((!prev && prev !== 0) ? 1 : prev);
const fibonacci = new InfiniteList(0, next);

// Take the first ten numbers from fibonacci series
log(fibonacci.take(10).map(x => x.value)); // -> [ 0, 1, 1, 2, 3, 5, 8, 13, 21, 34 ]

// What's the 50th item?
log(fibonacci.get(50).value); // -> 12586269025

// This is equivalent of the above! (modern browsers only!)
log(fibonacci[50].value); // -> 12586269025

// What's the next item?
log(fibonacci.get(50).next().value); // -> 20365011074

// What's 5 places after?
log(fibonacci.get(50).next(5).value); // -> 139583862445

// To Infinity and beyond!
log(fibonacci.last().value); // -> Infinity