effect-io-ai

Package: effect
Module: Effect

Effect.map

Transforms the value inside an effect by applying a function to it.

When to use

Use to transform an effect’s success value with a function that returns a plain value, producing a new effect without changing the original effect’s typed error or context requirements.

Details

map takes a function and applies it to the value contained within an effect, creating a new effect with the transformed value.

It’s important to note that effects are immutable, meaning that the original effect is not modified. Instead, a new effect is returned with the updated value.

Example (Choosing map syntax variants)

import { Effect, pipe } from "effect"

const myEffect = Effect.succeed(1)
const transformation = (n: number) => n + 1

const mappedWithPipe = pipe(myEffect, Effect.map(transformation))
const mappedWithDataFirst = Effect.map(myEffect, transformation)
const mappedWithMethod = myEffect.pipe(Effect.map(transformation))

Example (Adding a service charge)

import { Effect, pipe } from "effect"

const addServiceCharge = (amount: number) => amount + 1

const fetchTransactionAmount = Effect.promise(() => Promise.resolve(100))

const finalAmount = pipe(
  fetchTransactionAmount,
  Effect.map(addServiceCharge)
)

Effect.runPromise(finalAmount).then(console.log)
// Output: 101

See

• mapError for a version that operates on the error channel.
• mapBoth for a version that operates on both channels.
• flatMap or andThen for a version that can return a new effect.

Signature

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

Source

Since v2.0.0