JavaScript lazy arrays, sort of like Clojure's seqs

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JavaScript lazy arrays, sort of like Clojure's seqs. Lazy sequences can be thought of being a bit like a traditional Lisp cons cell.

# Fetch the dependencies.
npm install

# Run the tests.
npm test

Check the tests and source (lazy-array.js) JSDoc for more information, here's a quick example.

var larr = require('lazy-array');

var plainArray = ['foo', 'bar', 'baz'];

 * Creates a lazy sequence of all integers greater or equal to n.
 * @param {Number} n Starting integer.
 * @return {LazySequence}
function positiveNumbers(n) {
    return larr.create(function () {
        return larr.cons(n, positiveNumbers(n + 1));

// The functions work on plain arrays since they're all built on the core seq
// functions (cons, first and rest) which work on plain or lazy arrays.
larr.first(plainArray); // 'foo'; // ['bar', 'baz'];
larr.cons('pre', plainArray); // ['pre', 'foo', 'bar', 'baz']

// Allows you to operate on infinite sequences of values which are only
// calculated when requested.
larr.nth(positiveNumbers(10), 15); // 25

// You can take sections of that sequence and evaluate it to a plain array.
var nums = positiveNumbers(1);
larr.all(larr.take(3, larr.drop(5, nums))); // [6, 7, 8]

The script is wrapped in a UMD so you can require it with RequireJS or node.


Find the full unlicense in the UNLICENSE file, but here's a snippet.

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or distribute this software, either in source code form or as a compiled binary, for any purpose, commercial or non-commercial, and by any means.

Do what you want. Learn as much as you can. Unlicense more software.