<K, V>(self: HashMap<K, V>): IterableIterator<K>Returns an IterableIterator of the keys within the HashMap.
Example (Iterating keys)
import { HashMap } from "effect"
const map = HashMap.make(["a", 1], ["b", 2], ["c", 3])
const keys = Array.from(HashMap.keys(map))
console.log(keys.sort()) // ["a", "b", "c"]getters
Source effect/HashMap.ts:5441 lines
export const const keys: <K, V>(
self: HashMap<K, V>
) => IterableIterator<K>
Returns an IterableIterator of the keys within the HashMap.
Example (Iterating keys)
import { HashMap } from "effect"
const map = HashMap.make(["a", 1], ["b", 2], ["c", 3])
const keys = Array.from(HashMap.keys(map))
console.log(keys.sort()) // ["a", "b", "c"]
keys: <function (type parameter) K in <K, V>(self: HashMap<K, V>): IterableIterator<K>K, function (type parameter) V in <K, V>(self: HashMap<K, V>): IterableIterator<K>V>(self: HashMap<K, V>(parameter) self: {
pipe: { <A>(this: A): A; <A, B = never>(this: A, ab: (_: A) => B): B; <A, B = never, C = never>(this: A, ab: (_: A) => B, bc: (_: B) => C): C; <A, B = never, C = never, D = never>(this: A, ab: (_: A) => B, bc: (_: B) => C, cd: (_: C) => D): D; <…;
toString: () => string;
toJSON: () => unknown;
}
interface HashMap<out Key, out Value>A HashMap is an immutable key-value data structure that provides efficient lookup,
insertion, and deletion operations. It uses a Hash Array Mapped Trie (HAMT) internally
for structural sharing and optimal performance.
Example (Using basic HashMap operations)
import { HashMap } from "effect"
// Create a HashMap
const map = HashMap.make(["a", 1], ["b", 2], ["c", 3])
// Access values
const valueA = HashMap.get(map, "a") // Option.some(1)
const valueD = HashMap.get(map, "d") // Option.none()
// Check if key exists
console.log(HashMap.has(map, "b")) // true
// Add/update values (returns new HashMap)
const updated = HashMap.set(map, "d", 4)
console.log(HashMap.size(updated)) // 4
The HashMap namespace contains type-level utilities and helper types
for working with HashMap instances.
Example (Extracting HashMap types)
import { HashMap } from "effect"
// Create a concrete HashMap for type extraction
const inventory = HashMap.make(
["laptop", { quantity: 5, price: 999 }],
["mouse", { quantity: 20, price: 29 }]
)
// Extract types for reuse
type ProductId = HashMap.HashMap.Key<typeof inventory> // string
type Product = HashMap.HashMap.Value<typeof inventory> // { quantity: number, price: number }
type InventoryEntry = HashMap.HashMap.Entry<typeof inventory> // [string, Product]
// Use extracted types in functions
const updateInventory = (id: ProductId, product: Product) =>
HashMap.set(inventory, id, product)
const processEntry = ([id, product]: InventoryEntry) =>
`${id}: ${product.quantity} @ $${product.price}`
// Example of extracted types in action
const newProduct: Product = { quantity: 10, price: 199 }
const updatedInventory = updateInventory("tablet", newProduct)
HashMap<function (type parameter) K in <K, V>(self: HashMap<K, V>): IterableIterator<K>K, function (type parameter) V in <K, V>(self: HashMap<K, V>): IterableIterator<K>V>) => interface IterableIterator<T, TReturn = any, TNext = any>Describes a user-defined
Iterator
that is also iterable.
IterableIterator<function (type parameter) K in <K, V>(self: HashMap<K, V>): IterableIterator<K>K> = import internalinternal.const keys: <K, V>(
self: internal.HashMap<K, V>
) => IterableIterator<K>
Referenced by 1 symbols