audit

Audit operator based on a trigger stream. Only emits the latest resolved value from the source stream when the trigger is activated.

Type Definition

type audit = <T>(
  trigger$: Stream | Observable,
  shouldAwait?: boolean
) => (observable$: Observable<T>) => Observable<T>

Parameters

• trigger$ (Stream | Observable): The trigger stream. When this stream emits a value, the operator emits the latest resolved value from the source stream.
• shouldAwait (boolean, optional): Whether to wait for the source stream's pending state to finish. Defaults to true. When trigger$ fires while the source is pending, it waits for resolution before emitting.

Details

• Only emits the current value of the source stream when the trigger stream is in resolve status and emits a value.
• Only emits resolved values; rejected values are ignored.
• If the source stream emits multiple values quickly, only the latest resolved value is emitted.
• When shouldAwait is true, if the source is pending, it waits for resolution before emitting.
• When the trigger$ stream completes, the stream produced by audit also completes.

Usage Scenarios

Scenario 1: Basic trigger emission

import { $, audit } from 'fluth'

const source$ = $()
const trigger$ = $()

const audited$ = source$.pipe(audit(trigger$))

audited$.then((value) => {
  console.log('audited:', value)
})

// Set values on the source stream, but they are not emitted immediately
source$.next(1)
source$.next(2)
source$.next(3)

// Only emits the latest value when the trigger is activated
trigger$.next('trigger') // Output: audited: 3

Scenario 2: Handling rapidly changing data

import { $, audit } from 'fluth'

const searchInput$ = $()
const searchTrigger$ = $()

const searchResults$ = searchInput$.pipe(audit(searchTrigger$))

searchResults$.then((keyword) => {
  console.log('Search keyword:', keyword)
})

// User types quickly
searchInput$.next('a')
searchInput$.next('ap')
searchInput$.next('app')
searchInput$.next('apple')

// Only emits the latest search keyword when triggered
searchTrigger$.next('search') // Output: Search keyword: apple

Scenario 3: Awaiting asynchronous values

import { $, audit } from 'fluth'

const source$ = $()
const trigger$ = $()

// shouldAwait is true (default)
const audited$ = source$.pipe(audit(trigger$, true))

audited$.then((value) => {
  console.log('audited:', value)
})

// Send a Promise that resolves after some time
const slowPromise = new Promise((resolve) => {
  setTimeout(() => resolve('async result'), 1000)
})
source$.next(slowPromise)

// Trigger immediately, but will wait for the Promise to resolve
trigger$.next('trigger')
// After 1 second: Output: audited: async result

Scenario 4: Not awaiting asynchronous values

import { $, audit } from 'fluth'

const source$ = $()
const trigger$ = $()

// shouldAwait is false
const audited$ = source$.pipe(audit(trigger$, false))

audited$.then((value) => {
  console.log('audited:', value)
})

const slowPromise = new Promise((resolve) => {
  setTimeout(() => resolve('async result'), 1000)
})
source$.next(slowPromise)

// Trigger immediately, does not wait for the Promise to resolve
trigger$.next('trigger') // Output: audited: undefined