@most/index

Index and count events. More generally, pair events with any iterative value.

import { index, count } from '@most/index'
import { Stream, periodic } from '@most/core'

// 0 1 2 3 4 ...
const si: Stream<number> = index(periodic(1000))

// 1 2 3 4 5 ...
const sc: Stream<number> = count(periodic(1000))

Get it

npm install --save @most/index

API

count :: Stream a → Stream number

Count events.

// 1 2 3 ...
count(periodic(1000))

withCount :: Stream a → Stream [number, a]

Pair events with a 1-based count.

// [1, 'withCount'] [2, 'withCount'] [3, 'withCount'] ...
withCount(constant('withCount', periodic(1000)))

index :: Stream a → Stream number

Index events.

// 0 1 2 ...
index(periodic(1000))

withIndex :: Stream a → Stream [number, a]

Pair events with a 0-based index.

// [0, 'withIndex'] [1, 'withIndex'] [2, 'withIndex'] ...
withIndex(constant('withIndex', periodic(1000)))

withIndexStart :: number → Stream a → Stream [number, a]

Pair events with a start-based index.

// [100, 'withIndexStart'] [101, 'withIndexStart'] [102, 'withIndexStart'] ...
withIndexStart(100, constant('withIndexStart', periodic(1000)))

indexed :: (s → [i, s]) → s → Stream a → Stream [i, a]

Pair events with any iteratively computed index.

const stringIndex = (s: string) => (prev: string): [string, string] =>
  [prev, prev + s]

// ['', 'indexed'], ['a', 'indexed'], ['aa', 'indexed'], ['aaa', 'indexed']
indexed(stringIndex('a'), '', constant('indexed', periodic(1000)))