Obliterator

Obliterator is a dead simple JavaScript/TypeScript library providing miscellaneous higher-order iterator/iterable functions such as combining two or more iterators into a single one.

Note that when possible, obliterator also consider sequences such as arrays, strings etc. as valid iterables (although they are not proper ES6 iterables values), for convenience.

Installation

npm install --save obliterator

Note that obliterator comes along with its TypeScript declarations.

Usage

Summary

Classes

• Iterator

Functions

• chain
• combinations
• consume
• every
• filter
• find
• forEach
• forEachWithNullKeys
• includes
• iter
• map
• match
• permutations
• powerSet
• some
• split
• take

Iterator

A handy Iterator class easily usable with ES2015's for ... of loop constructs & spread operator.

import Iterator from 'obliterator/iterator';
// Or
import {Iterator} from 'obliterator';

const iterator = new Iterator(function () {
  // Define what the `next` function does
  return {done: false, value: 34};
});

// Checking that the given value is an iterator (native or else)
Iterator.is(value);

// Creating an empty iterator
const emptyIterator = Iterator.empty();

// Creating a simple iterator from a single value
const simpleIterator = Iterator.of(34);

// Creating a simple iterator from multiple values
const multipleIterator = Iterator.of(1, 2, 3);

chain

Variadic function chaining all the given iterable-like values.

import chain from 'obliterator/chain';
// Or
import {chain} from 'obliterator';

const set1 = new Set('a');
const set2 = new Set('bc');

const chained = chain(set1.values(), set2);

chained.next();
>>> {done: false, value: 'a'}
chained.next();
>>> {done: false, value: 'b'}

combinations

Returns an iterator of combinations of the given array and of the given size.

Note that for performance reasons, the yielded combination is always the same object.

import combinations from 'obliterator/combinations';
// Or
import {combinations} from 'obliterator';

const iterator = combinations(['A', 'B', 'C', 'D'], 2);

iterator.next().value;
>>> ['A', 'B']
iterator.next().value;
>>> ['A', 'C']

consume

Function consuming the given iterator fully or for n steps.

import consume from 'obliterator/consume';
// Or
import {consume} from 'obliterator';

const set = new Set([1, 2, 3]);

// Consuming the whole iterator
let iterator = set.values();
consume(iterator);
iterator.next().done >>> true;

// Consuming n steps
let iterator = set.values();
consume(iterator, 2);
iterator.next().value >>> 3;

every

Function returning whether all items of an iterable-like match the given predicate function.

import every from 'obliterator/every';
// Or
import {every} from 'obliterator';

every([2, 4, 6], n => n % 2 === 0);
>>> true

every([1, 2, 3], n => n % 2 === 0);
>>> false

filter

Function returning an iterator filtering another one's values using the given predicate function.

import filter from 'obliterator/filter';
// Or
import {filter} from 'obliterator';

const set = new Set([1, 2, 3, 4, 5]);

const even = x => x % 2 === 0;

const iterator = filter(set.values(), even);

iterator.next().value >>> 2;
iterator.next().value >>> 4;

find

Function returning the next item matching given predicate function in an iterable-like.

import find from 'obliterator/find';
// Or
import {find} from 'obliterator';

const set = new Set([1, 2, 3, 4, 5]);

const even = x => x % 2 === 0;

const values = set.values();

find(values, even);
>>> 2

find(values, even);
>>> 4

find(values, even);
>>> undefined

forEach

Function able to iterate over almost any JavaScript iterable value using a callback.

Supported values range from arrays, typed arrays, sets, maps, objects, strings, arguments, iterators, arbitrary iterables etc.

import forEach from 'obliterator/foreach';
// Or
import {forEach} from 'obliterator';

const set = new Set(['apple', 'banana']);

forEach(set.values(), (value, i) => {
  console.log(i, value);
});

// Iterating over a string
forEach('abc', (char, i) => ...);

// Iterating over a map
forEach(map, (value, key) => ...);

forEachWithNullKeys

Variant of forEach one can use to iterate over mixed values but with the twist that iterables without proper keys (lists, sets etc.), will yield null instead of an index key.

Supported values range from arrays, typed arrays, sets, maps, objects, strings, arguments, iterators, arbitrary iterables etc.

import {forEachWithNullKeys} from 'obliterator/foreach';

const set = new Set(['apple', 'banana']);

forEach(set, (value, key) => {
  console.log(key, value);
});
>>> null, 'apple'
>>> null, 'banana'

includes

Function returning whether the given value can be found in given iterable-like.

import {includes} from 'obliterator';
// Or
import includes from 'obliterator/includes';

includes([1, 2, 3], 3);
>>> true;

includes('test', 'a');
>>> false;

iter

Function casting any iterable-like value to a proper iterator. Will throw an error if the given value cannot be cast as an iterator.

import {iter} from 'obliterator';
// Or
import iter from 'obliterator/iter';

iter('test');
iter(new Set([1, 2, 3]));

// This will throw:
iter(null);

map

Function returning an iterator mapping another one's values using the given function.

import map from 'obliterator/map';
// Or
import {map} from 'obliterator';

const set = new Set([1, 2, 3, 4, 5]);

const triple = x => x * 3;

const iterator = map(set.values(), triple);

iterator.next().value >>> 3;
iterator.next().value >>> 6;

match

Function returning an iterator over the matches of a given regex applied to the target string.

import match from 'obliterator/match';
// Or
import {match} from 'obliterator';

const iterator = match(/t/, 'test');

iterator.next().value.index >>> 0;
iterator.next().value.index >>> 3;

permutations

Returns an iterator of permutations of the given array and of the given size.

Note that for performance reasons, the yielded permutation is always the same object.

import permutations from 'obliterator/permutations';
// Or
import {permutations} from 'obliterator';

let iterator = permutations([1, 2, 3]);

iterator.next().value
>>> [1, 2, 3]
iterator.next().value
>>> [1, 3, 2]

iterator = permutations(['A', 'B', 'C', 'D'], 2);

iterator.next().value;
>>> ['A', 'B']
iterator.next().value;
>>> ['A', 'C']

powerSet

Returns an iterator of sets composing the power set of the given array.

import powerSet from 'obliterator/power-set';
// Or
import {powerSet} from 'obliterator';

const iterator = powerSet(['A', 'B', 'C']);

iterator.next().value;
>>> []
iterator.next().value;
>>> ['A']

some

Returns whether the given iterable-like has some item matching the given predicate function.

import some from 'obliterator/some';
// Or
import {some} from 'obliterator';

some(new Set([1, 2, 3]), n => n % 2 === 0);
>>> true

some('test', c => c === 'a');
>>> false

split

Returns an iterator over the splits of the target string, according to the given RegExp pattern.

import split from 'obliterator/split';
// Or
import {split} from 'obliterator';

const iterator = split(/;/g, 'hello;world;super');

iterator.next().value;
>>> 'hello'
iterator.next().value;
>>> 'world'

take

Function taking values from given iterator and returning them in an array.

import take from 'obliterator/take';
// Or
import {take} from 'obliterator';

const set = new Set([1, 2, 3]);

// To take n values from the iterator
take(set.values(), 2);
>>> [1, 2]

// To convert the full iterator into an array
take(set.values());
>>> [1, 2, 3]

Contribution

Contributions are obviously welcome. Please be sure to lint the code & add the relevant unit tests before submitting any PR.

git clone [email protected]:Yomguithereal/obliterator.git
cd obliterator
npm install

# To lint the code
npm run lint

# To run the unit tests
npm test

License

MIT