effect-io-ai

Package: effect
Module: MutableHashMap

MutableHashMap.modifyAt

Updates or removes the specified key using a function from the current optional value to the next optional value.

When to use

Use to decide whether to insert, update, or remove a key based on its current optional value.

Example (Updating or removing a key)

import { MutableHashMap, Option } from "effect"

const map = MutableHashMap.make(["count", 5])

// Update existing key
MutableHashMap.modifyAt(
  map,
  "count",
  (option) => Option.map(option, (n) => n * 2)
)
console.log(MutableHashMap.get(map, "count")) // Some(10)

// Add new key
MutableHashMap.modifyAt(
  map,
  "new",
  (option) => Option.isNone(option) ? Option.some(42) : option
)
console.log(MutableHashMap.get(map, "new")) // Some(42)

// Remove key by returning None
MutableHashMap.modifyAt(map, "count", () => Option.none())
console.log(MutableHashMap.has(map, "count")) // false

// Conditional update
MutableHashMap.modifyAt(
  map,
  "new",
  (option) => Option.filter(option, (n) => n > 50) // Remove if <= 50
)
console.log(MutableHashMap.has(map, "new")) // false (42 <= 50)

See

• modify for updating only when the key already exists
• set for inserting or replacing directly
• remove for deleting directly

Signature

declare const modifyAt: { <K, V>(key: K, f: (value: Option.Option<V>) => Option.Option<V>): (self: MutableHashMap<K, V>) => MutableHashMap<K, V>; <K, V>(self: MutableHashMap<K, V>, key: K, f: (value: Option.Option<V>) => Option.Option<V>): MutableHashMap<K, V>; }

Source

Since v2.0.0