IterableFu

IterableFu is a small (1.2kb minimized and gzipped) library of functions like range, map, reduce, filter, zip, for iterable objects.

IterableFu has a chainable class to make it easy to chain iterable transforms. There is a chainable class factory makeChainableIterable, so you easily can add methods, or reduce bundle size.

Features

• Chainable: chainable([0, 1, 2]).map(x => 2*x).toArray().
• Works with your generators (and iterables): chainable(yourGenerator()).mapWith(yourTransformGenerator).
• Customizable makeChainableIterable, to add methods or reduce bundle sizes.
• Functional API takes data last, so you can curry, pipe and compose with your functional library.
• Exports both CommonJS and ES modules - dual package.

If you want asynchronous iterables along with task pool, event queue, pub/sub, merge, chunk, throttle, and the like, checkout await-for-it.

Table of Contents

• Installation
• Getting Started
• API
• Examples
  • Basics
  • One Time Use
  • Iterablefu and Your Generators
• Smaller Bundles
• Customization
• Alternatives
• Contributing
• Issues
• License

Installation

npm install --save iterablefu

Getting Started

If you want the chainable API, use this import.

import { chainable } from 'iterablefu'

import { chainable } from 'iterablefu'

const iterable = chainable([1, 2, 3, 4, 5, 6]) // <-- throw any synchronous iterable in here
  .filter(x => x % 2 === 0) // filters out odd numbers
  .map(x => 2 * x)

console.log(Array.from(iterable)) // prints [4, 8, 12]

The most used methods are probably: zip, zipAll, filter, flatten, map, and reduce. The documentation has an example for each method:

• chainable- Is a factory that starts the chain and produces a ChainableIterable
• ChainableIterable - For all the transforms and reducer methods

If you want the functional API, use this import.

import { generators, transforms, reducers } from 'iterablefu'

You may also specify the modules directly to reduce bundle sizes. See more in the Smaller Bundles section.

API

• Chainable API
  • Chainable factory, factory functions that produce ChainableIterable instances
  • ChainableIterable, chainable iterable generators, transforms, and reducers
  • Custom chainables, create custom chainable iterables
• Functional API
  • Generators, generator functions to create iterable sequences
  • Transforms, functions to convert an iterable into another iterable (e.g. map, filter)
  • Reducers, functions to convert an iterable into a value

Examples

Basics

IterableFu provides three basic categories of functions:

• Generators - create an iterable sequence
• Transforms - convert one iterable sequence into another
• Reducers - convert an iterable sequence into a value

Here's a quick example showing range (a generator), map (a transform), and reduce (a reducer).

import { chainable } from 'iterablefu'
const answer =
  chainable
    .range(5) // generates 0, 1, 2, 3, 4
    .map(x => 2 * x) // maps to 0, 2, 4, 6, 8
    .reduce((a, x) => a + x, 0) // 0 + 2 + 4 + 6 + 8 = 20
console.log(answer) // prints 20

Some generators can convert Arrays or any other iterable into chainable iterables.

const d = chainable([1, 2, 3]) // makes a chainable version of [1, 2, 3]
const e = chainable.concatenate([0, 1, 2], [3, 4]) // becomes [0, 1, 2, 3, 4]
const f = chainable.zip([1, 2, 3], ['a', 'b', 'c']) // becomes [[1, 'a'], [2, 'b'], [3, 'c']]

There are several ways to convert back to Arrays.

const a = Array.from(chainable.range(5)) // a has the value [0, 1, 2, 3, 4, 5]
const b = [...chainable.range(3)] // b has the value [0, 1, 2]
const c = chainable.range(2, 5).toArray() // c has the value [2, 3, 4, 5, 6]

One Time Use

Except for one method, repeatIterable, IterableFu only supports one-time iteration. This is because iterators cannot be reused once done.

An iterable class like Array, can be iterated more than once because it produces a new iterator for each iteration.

// IterableFu produces one-time use sequences
const a = chainable.range(5)
console.log([...a]) // print [0, 1, 2, 3, 4], iterator is now done
console.log([...a]) // prints [] because the iterator was done before the call

To reuse an IterableFu chain, wrap it in a function so that a new Generator object is returned each time it is called.

const fn = () => chainable.range(5)
// Note the function calls below...
console.log([...fn()]) // prints [0, 1, 2, 3, 4]
console.log([...fn()]) // prints [0, 1, 2, 3, 4] because a new iterator was used

Iterablefu and Your Generators

To use a generator function that creates a sequence, use chainable as a function.

// A simple generator function
const fn = function * (length) {
  for (let i = 0; i < length; i++) {
    yield i
  }
}
// be sure to call the generator, don't just pass the function
const a = chainable(fn(3))
console.log([...a]) // prints [0, 1, 2]

To use a generator that transforms a sequence, use mapWith.

// An example generator that transforms another sequence.
const fn = function * (n, iterable) {
  for (let x of iterable) {
    yield n * x
  }
}
const input = [0, 1, 2, 3, 4]
// mapWith only accepts generator functions that have one parameter: iterable.
// If your generator takes additional parameters beyond iterable, you need
// to wrap it with another function that takes only one parameter. Like this:
const wrapper = (iterable) => fn(3, iterable)
const a = chainable(input).mapWith(wrapper).toArray()
console.log(a) // prints [0, 3, 6, 9, 12]

Smaller Bundles

You can potentially reduce bundle size by importing the generators and function you want to use directly.

import { zip, zipAll } from 'iterablefu/src/generators.js'
import { filter, flatten, map } from 'iterablefu/src/transfroms.js'
import { reduce } from 'iterablefu/src/reducers.js'

If you want a reduced size chainable object, use makeChainableIterable with the directly imported functions. Customization is covered more completely in the makeChainableIterable docs.

// using the imports from above
import { makeChainableIterable } from 'iterablefu/src/makechainable.js'
const generators = { zip, zipAll }
const transforms = { filter, flatten, map }
const reducers = { reduce }
const chainable = makeChainableIterable(generators, transforms, reducers)

Customization

Customization is covered in the makeChainableIterable documentation.

Alternatives

There are lots of alternatives:

• wu - has many more methods than IterableFu. Does not use ES6 modules.
• itiri - many functions that force conversion to array. Typescript.
• lazy.js - more methods, does not use generators
• linq.js - LINQ (a .NET library) for JavaScript
• GenSequence - similar to IterableFu. Typescript.

... and many more.

Contributing

Contributions are welcome. Please create a pull request.

I use pnpm instead of npm.

Automated browser tests use electron. Automated package tests build a *.tgz package and run tweaked unit tests in a temporary directory. Use pnpm run build to run everything in the right order.

Issues

This project uses Github issues.

License

MIT