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variable / @typed/fx/Fx

exhaustLatestMap

Maps each element to an inner Fx, running one now and retaining only the latest waiting value.

Package version
2.0.0-beta.7
Category
Concurrent work
Since
1.0.0

Follow one execution

Maps each element to an inner Fx, running one now and retaining only the latest waiting value.

Fx timelineexhaustLatestMap keeps only the newest value waiting behind active workexhaustLatestMap
OperatorexhaustLatestMap(index)
Read this diagram

Follow each lane from left to right. Events stacked vertically share a tick; the green cursor marks the current time across every lane.

  • A value
    The text inside the pill is the emitted value.
  • Work starts
    The raised chevron starts an inner run (^ in the source).
  • The run returns
    The vertical bar ends this lane’s run.
  • A cause is delivered
    The exclamation mark belongs to this lane.
  • Work is interrupted
    The cross marks cancellation of this run.
  • Current time
    The line and diamond move together across all lanes.
  • Happening now
    A highlighted event is at the current tick.
  • Still ahead
    Muted, dashed values have not happened yet.
  • Time continues
    The lane’s arrow is not a return marker. An empty stretch can be quiet work that is still running.

Illustrated ticks start at 0. At 1×, one illustrated tick takes one second; captions specify real durations when timing matters. A cause or interruption belongs to its lane, and other work may continue. Scroll horizontally to inspect the rest of a long timeline.

Source and admitted-inner failures are forwarded and both environments remain typed. The required Scope owns every active inner fiber. Source completion waits until the active and final pending inner finish; interruption closes the Scope and runs inner finalizers. The one-slot pending buffer retains work, not emitted output.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

import { exhaustLatestMap } from "@typed/fx/Fx";

Signatures

export declare const exhaustLatestMap: FlatMapLike;

Why

exhaustLatestMap fits work that cannot overlap but must eventually reflect the newest request. Unlike {@link exhaustMap }, it remembers one pending value; unlike {@link concatMap }, it does not let a backlog grow.

Admission, buffering, and cardinality

The first value while idle starts immediately. While that inner runs, each new value replaces the single pending inner Effect; replaced values never run. When the active inner completes, the latest pending inner starts. An admitted inner may emit any number of values, in that inner’s order.

Ownership and lifetime

Source and admitted-inner failures are forwarded and both environments remain typed. The required Scope owns every active inner fiber. Source completion waits until the active and final pending inner finish; interruption closes the Scope and runs inner finalizers. The one-slot pending buffer retains work, not emitted output.

Examples

import { Fx } from "@typed/fx"
import { Effect } from "effect"

const refreshes = Fx.mergeAll(
  Fx.at("v1", "0 millis"),
  Fx.at("v2", "5 millis"),
  Fx.at("v3", "10 millis")
)
const latestEventually = Fx.exhaustLatestMap(refreshes, (version) =>
  Fx.at(`indexed:${version}`, "20 millis")
)

Effect.runPromise(Effect.scoped(Fx.collectAll(latestEventually))).then(console.log)
// ["indexed:v1", "indexed:v3"]

Other public imports

These import paths expose the same declaration. Each page retains its own public name and signature.

Source