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variable / @typed/fx/Fx

map

Transforms the elements of an Fx using a provided function.

Package version
2.0.0-beta.7
Category
Transforming values
Since
1.0.0

Follow one execution

A synchronous mapping emits one transformed value for every input.

Fx timelinemap(n => n * 10)map
Operatormap(n => n * 10)
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.

This operation acquires no resources and retains no state. Running the result runs the source in the same Scope, and interruption or failure is forwarded unchanged.

Source implementation · Learn the surrounding model

Compare all Fx timelines →

Import

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

Signatures

export declare const map: {
    <A, B>(f: (a: A) => B): <E, R>(self: Fx<A, E, R>) => Fx<B, E, R>;
    <A, E, R, B>(self: Fx<A, E, R>, f: (a: A) => B): Fx<B, E, R>;
};

Why

map changes each pushed value without changing when values arrive. It emits exactly once for every upstream success, in upstream order; the callback is synchronous and cannot add failures or services.

Ownership and lifetime

This operation acquires no resources and retains no state. Running the result runs the source in the same Scope, and interruption or failure is forwarded unchanged.

Examples

import { Fx } from "@typed/fx"

const labels = Fx.fromIterable([1, 2, 3]).pipe(Fx.map((n) => `item-${n}`))

Other public imports

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

Source