<K extends string, A, B extends A>(
refinement: (a: NoInfer<A>, key: K) => a is B
): (
self: ReadonlyRecord<K, A>
) => Record<ReadonlyRecord.NonLiteralKey<K>, B>
<K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (
self: ReadonlyRecord<K, A>
) => Record<ReadonlyRecord.NonLiteralKey<K>, A>
<K extends string, A, B extends A>(
self: ReadonlyRecord<K, A>,
refinement: (a: A, key: K) => a is B
): Record<ReadonlyRecord.NonLiteralKey<K>, B>
<K extends string, A>(
self: ReadonlyRecord<K, A>,
predicate: (a: A, key: K) => boolean
): Record<ReadonlyRecord.NonLiteralKey<K>, A>Selects properties from a record whose values match the given predicate.
Example (Filtering record values)
import { Record } from "effect"
import * as assert from "node:assert"
const x = { a: 1, b: 2, c: 3, d: 4 }
assert.deepStrictEqual(Record.filter(x, (n) => n > 2), { c: 3, d: 4 })filtering
Source effect/Record.ts:77430 lines
export const const filter: {
<K extends string, A, B extends A>(
refinement: (a: NoInfer<A>, key: K) => a is B
): (
self: ReadonlyRecord<K, A>
) => Record<ReadonlyRecord.NonLiteralKey<K>, B>
<K extends string, A>(
predicate: (A: NoInfer<A>, key: K) => boolean
): (
self: ReadonlyRecord<K, A>
) => Record<ReadonlyRecord.NonLiteralKey<K>, A>
<K extends string, A, B extends A>(
self: ReadonlyRecord<K, A>,
refinement: (a: A, key: K) => a is B
): Record<ReadonlyRecord.NonLiteralKey<K>, B>
<K extends string, A>(
self: ReadonlyRecord<K, A>,
predicate: (a: A, key: K) => boolean
): Record<ReadonlyRecord.NonLiteralKey<K>, A>
}
Selects properties from a record whose values match the given predicate.
Example (Filtering record values)
import { Record } from "effect"
import * as assert from "node:assert"
const x = { a: 1, b: 2, c: 3, d: 4 }
assert.deepStrictEqual(Record.filter(x, (n) => n > 2), { c: 3, d: 4 })
filter: {
<function (type parameter) K in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>K extends string, function (type parameter) A in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>A, function (type parameter) B in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>B extends function (type parameter) A in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>A>(
refinement: (a: NoInfer<A>, key: K) => a is Brefinement: (a: NoInfer<A>a: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>A>, key: K extends stringkey: function (type parameter) K in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>K) => a: NoInfer<A>a is function (type parameter) B in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>B
): (self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>K, function (type parameter) A in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>A>) => type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<ReadonlyRecord.type ReadonlyRecord<in out K extends string | symbol, out A>.NonLiteralKey<K extends string | symbol> = K extends string ? ReadonlyRecord.IsFiniteString<K> extends true ? string : K : symbolRepresents a type that converts literal string keys to generic string type and symbol keys to generic symbol type.
This is useful for maintaining type safety while allowing flexible key types in record operations.
Example (Converting literal keys to non-literal keys)
import type { Record } from "effect"
// For literal string keys, this becomes 'string'
type Example1 = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// For symbol keys, this becomes 'symbol'
type Example2 = Record.ReadonlyRecord.NonLiteralKey<symbol> // symbol
NonLiteralKey<function (type parameter) K in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>K>, function (type parameter) B in <K extends string, A, B extends A>(refinement: (a: NoInfer<A>, key: K) => a is B): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, B>B>
<function (type parameter) K in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>K extends string, function (type parameter) A in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>A>(
predicate: (A: NoInfer<A>, key: K) => booleanpredicate: (type A: NoInfer<A>A: type NoInfer<A> = [A][A extends any ? 0 : never]Prevents TypeScript from inferring a type parameter from a specific
position.
When to use
Use when a function parameter must match an inferred type without becoming
an inference source.
Details
The parameter using NoInfer must still match the inferred type.
Example (Controlling inference)
import type { Types } from "effect"
declare function withDefault<T>(value: T, fallback: Types.NoInfer<T>): T
// T is inferred as "a" | "b" from the first argument only
const result = withDefault<"a" | "b">("a", "b")
NoInfer<function (type parameter) A in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>A>, key: K extends stringkey: function (type parameter) K in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>K) => boolean
): (self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>K, function (type parameter) A in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>A>) => type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<ReadonlyRecord.type ReadonlyRecord<in out K extends string | symbol, out A>.NonLiteralKey<K extends string | symbol> = K extends string ? ReadonlyRecord.IsFiniteString<K> extends true ? string : K : symbolRepresents a type that converts literal string keys to generic string type and symbol keys to generic symbol type.
This is useful for maintaining type safety while allowing flexible key types in record operations.
Example (Converting literal keys to non-literal keys)
import type { Record } from "effect"
// For literal string keys, this becomes 'string'
type Example1 = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// For symbol keys, this becomes 'symbol'
type Example2 = Record.ReadonlyRecord.NonLiteralKey<symbol> // symbol
NonLiteralKey<function (type parameter) K in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>K>, function (type parameter) A in <K extends string, A>(predicate: (A: NoInfer<A>, key: K) => boolean): (self: ReadonlyRecord<K, A>) => Record<ReadonlyRecord.NonLiteralKey<K>, A>A>
<function (type parameter) K in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>K extends string, function (type parameter) A in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>A, function (type parameter) B in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>B extends function (type parameter) A in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>A>(
self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>K, function (type parameter) A in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>A>,
refinement: (a: A, key: K) => a is Brefinement: (a: Aa: function (type parameter) A in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>A, key: K extends stringkey: function (type parameter) K in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>K) => a: Aa is function (type parameter) B in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>B
): type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<ReadonlyRecord.type ReadonlyRecord<in out K extends string | symbol, out A>.NonLiteralKey<K extends string | symbol> = K extends string ? ReadonlyRecord.IsFiniteString<K> extends true ? string : K : symbolRepresents a type that converts literal string keys to generic string type and symbol keys to generic symbol type.
This is useful for maintaining type safety while allowing flexible key types in record operations.
Example (Converting literal keys to non-literal keys)
import type { Record } from "effect"
// For literal string keys, this becomes 'string'
type Example1 = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// For symbol keys, this becomes 'symbol'
type Example2 = Record.ReadonlyRecord.NonLiteralKey<symbol> // symbol
NonLiteralKey<function (type parameter) K in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>K>, function (type parameter) B in <K extends string, A, B extends A>(self: ReadonlyRecord<K, A>, refinement: (a: A, key: K) => a is B): Record<ReadonlyRecord.NonLiteralKey<K>, B>B>
<function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K extends string, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A>(
self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A>,
predicate: (a: A, key: K) => booleanpredicate: (a: Aa: function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A, key: K extends stringkey: function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K) => boolean
): type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<ReadonlyRecord.type ReadonlyRecord<in out K extends string | symbol, out A>.NonLiteralKey<K extends string | symbol> = K extends string ? ReadonlyRecord.IsFiniteString<K> extends true ? string : K : symbolRepresents a type that converts literal string keys to generic string type and symbol keys to generic symbol type.
This is useful for maintaining type safety while allowing flexible key types in record operations.
Example (Converting literal keys to non-literal keys)
import type { Record } from "effect"
// For literal string keys, this becomes 'string'
type Example1 = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// For symbol keys, this becomes 'symbol'
type Example2 = Record.ReadonlyRecord.NonLiteralKey<symbol> // symbol
NonLiteralKey<function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K>, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A>
} = import dualdual(
2,
<function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K extends string, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A>(
self: ReadonlyRecord<K, A>self: type ReadonlyRecord<in out K extends string | symbol, out A> = { readonly [P in K]: A; }Represents a readonly record with keys of type K and values of type A.
This is the foundational type for immutable key-value mappings in Effect.
Example (Defining a readonly record type)
import type { Record } from "effect"
// Creating a readonly record type
type UserRecord = Record.ReadonlyRecord<"name" | "age", string | number>
const user: UserRecord = {
name: "John",
age: 30
}
Namespace containing utility types for working with readonly records.
These types help with type-level operations on record keys and values.
Example (Using readonly record helper types)
import type { Record } from "effect"
// Using NonLiteralKey to convert literal keys to generic types
type GenericKey = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// Using IntersectKeys to find common keys between record types
type CommonKeys = Record.ReadonlyRecord.IntersectKeys<"a" | "b", "b" | "c"> // "b"
ReadonlyRecord<function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A>,
predicate: (a: A, key: K) => booleanpredicate: (a: Aa: function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A, key: K extends stringkey: function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K) => boolean
): type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<ReadonlyRecord.type ReadonlyRecord<in out K extends string | symbol, out A>.NonLiteralKey<K extends string | symbol> = K extends string ? ReadonlyRecord.IsFiniteString<K> extends true ? string : K : symbolRepresents a type that converts literal string keys to generic string type and symbol keys to generic symbol type.
This is useful for maintaining type safety while allowing flexible key types in record operations.
Example (Converting literal keys to non-literal keys)
import type { Record } from "effect"
// For literal string keys, this becomes 'string'
type Example1 = Record.ReadonlyRecord.NonLiteralKey<"foo" | "bar"> // string
// For symbol keys, this becomes 'symbol'
type Example2 = Record.ReadonlyRecord.NonLiteralKey<symbol> // symbol
NonLiteralKey<function (type parameter) K in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>K>, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A> => {
const const out: Record<string, A>out: type Record<K extends keyof any, T> = {
[P in K]: T
}
Construct a type with a set of properties K of type T
Record<string, function (type parameter) A in <K extends string, A>(self: ReadonlyRecord<K, A>, predicate: (a: A, key: K) => boolean): Record<ReadonlyRecord.NonLiteralKey<K>, A>A> = const empty: <string, A>() => Record<
string,
A
>
Creates a new, empty record.
Example (Creating an empty record)
import { Record } from "effect"
// Create an empty record
const emptyRecord = Record.empty<string, number>()
console.log(emptyRecord) // {}
// The type ensures type safety for future operations
const withValue = Record.set(emptyRecord, "count", 42)
console.log(withValue) // { count: 42 }
empty()
for (const const key: K extends stringkey of const keys: <
K extends string | symbol,
A
>(
self: ReadonlyRecord<K, A>
) => Array<K & string>
Retrieves the keys of a given record as an array.
Example (Getting record keys)
import { Record } from "effect"
import * as assert from "node:assert"
assert.deepStrictEqual(Record.keys({ a: 1, b: 2, c: 3 }), ["a", "b", "c"])
keys(self: ReadonlyRecord<K, A>self)) {
if (predicate: (a: A, key: K) => booleanpredicate(self: ReadonlyRecord<K, A>self[const key: K extends stringkey], const key: K extends stringkey)) {
const out: Record<string, A>out[const key: K extends stringkey] = self: ReadonlyRecord<K, A>self[const key: K extends stringkey]
}
}
return const out: Record<string, A>out
}
)Referenced by 1 symbols