@bemoje/iter

Utility functions for working with iterables, especially map-like key-value pair structures.

Exports

• filterArray: Filter an array based on a predicate function.
• filterIterable: Filter an iterable based on a predicate function.
• filterIterableEntries: Filter an iterable of key-value entries based on a predicate function.
• filterIterableKeys: Filter an iterable of key-value entries based on a predicate function that tests keys.
• filterIterableValues: Filter an iterable of key-value entries based on a predicate function that tests values.
• filterMap: Filter a Map based on a predicate function.
• filterObject: Filter an object's properties based on a predicate function.
• filterSet: Filter a Set based on a predicate function.
• forEachArray: Execute a callback function for each element in an array.
• forEachIterable: Execute a callback function for each element in an iterable.
• forEachIterableEntries: Execute a callback function for each entry in a map-like iterable.
• forEachIterableKeys: Execute a callback function for each key in an iterable of key-value pairs.
• forEachIterableValues: Execute a callback function for each value in an iterable of key-value pairs.
• forEachMap: Execute a callback function for each entry in a Map.
• forEachObject: Execute a callback function for each property in an object.
• forEachSet: Execute a callback function for each value in a Set.
• mapArray: Transform each element in an array using a mapper function.
• mapIterable: Transform each element in an iterable using a mapper function.
• mapIterableEntries: Transform each entry in an iterable of key-value pairs using a mapper function.
• mapIterableKeys: Transform the keys in an iterable of key-value pairs using a mapper function.
• mapIterableValues: Transform the values in an iterable of key-value pairs using a mapper function.
• mapMap: Transform the values in a Map using a mapper function.
• mapObject: Transform the values in an object using a mapper function.
• mapSet: Transform each value in a Set using a mapper function.
• reduceArray: Reduce an array to a single value using a reducer function.
• reduceIterable: Reduce an iterable to a single value using a reducer function.
• reduceIterableEntries: Reduce an iterable of key-value entries to a single value using a reducer function.
• reduceIterableKeys: Reduce an iterable of key-value entries based on keys using a reducer function.
• reduceIterableValues: Reduce an iterable of key-value entries based on values using a reducer function.
• reduceMap: Reduce a Map to a single value using a reducer function.
• reduceObject: Reduce an object to a single value using a reducer function.
• reduceSet: Reduce a Set to a single value using a reducer function.
• toObjectIterable: Convert a map-like iterable to a regular object.

Installation

npm install @bemoje/iter

Usage

Transform Iterables

import { mapIterable, mapIterableKeys, mapIterableValues } from '@bemoje/iter'

const entries: Iterable<[string, number]> = new Map([
  ['a', 1],
  ['b', 2],
])

// Transform both keys and values
const mapped = mapIterable(entries, (value, key) => [key.toUpperCase(), value * 10])
// [['A', 10], ['B', 20]]

// Transform only keys
const newKeys = mapIterableKeys(entries, (key) => key.toUpperCase())
// [['A', 1], ['B', 2]]

// Transform only values
const doubled = mapIterableValues(entries, (value) => value * 2)
// [['a', 2], ['b', 4]]

Filter and Reduce

import { filterIterable, reduceIterable, forEachIterable } from '@bemoje/iter'

const entries: Iterable<[string, number]> = new Map([
  ['a', 1],
  ['b', 2],
  ['c', 3],
])

// Filter entries by value
const filtered = filterIterable(entries, (value) => value > 1)
// [['b', 2], ['c', 3]]

// Reduce to a single value
const sum = reduceIterable(entries, (acc, value) => acc + value, 0)
// 6

// Side effects
forEachIterable(entries, (value, key) => console.log(`${key}: ${value}`))

Count Unique Values

import { countUniques } from '@bemoje/iter'

const words = ['apple', 'banana', 'apple', 'cherry', 'banana', 'apple']
const counts = countUniques(words)
// ExtMap { 'apple' => 3, 'banana' => 2, 'cherry' => 1 } (sorted by count desc)

Convert to Object

import { toObjectIterable } from '@bemoje/iter'

const entries: Iterable<[string, number]> = [
  ['a', 1],
  ['b', 2],
]
const obj = toObjectIterable(entries)
// { a: 1, b: 2 }