Equality

Equality: object

Defined in: Core/Equality.ts:14

Type Declaration

and

and: <A>(other) => (equality) => Equality<A>

Combines two equalities with logical AND. Both must pass for two values to be considered equal. Data-last: the first equality is the data being piped.

Type Parameters

A

A

Parameters

other

Equality<A>

Returns

(equality) => Equality<A>

See

• Equality.by to project equality checks onto specific fields.
• Equality.struct for record-wide structural equality.

Example

const exact = pipe(byName, Equality.and(byRole));
exact(userA, userB); // true only if name AND role match

array

array: <A>(itemEquality) => Equality<readonly A[]>

Lifts an element equality into an array equality. Two arrays are equal if they have the same length and every element pair is equal under itemEquality.

Type Parameters

A

A

Parameters

itemEquality

Equality<A>

Returns

Equality<readonly A[]>

See

Equality.tuple for fixed-length positional array equality.

Example

Equality.array(Equality.number)([1, 2, 3], [1, 2, 3]); // true

boolean

boolean: Equality<boolean> = booleanEq

Equality for booleans.

See

Equality.string for primitive string equality.

Example

Equality.boolean(true, true); // true

by

by: <A, B>(extract) => (equality) => Equality<B>

Adapts an equality for type A into an equality for type B by extracting a field. Read as “equality by this field”: pipe(Equality.string, Equality.by(u => u.name)).

Type Parameters

A

A

B

B

Parameters

extract

(value) => A

Returns

(equality) => Equality<B>

See

• Equality.and to combine multiple equality checks.
• Equality.struct to check equality across multiple record fields.

Example

type Product = { id: string; price: number };
const byId = pipe(Equality.string, Equality.by((p: Product) => p.id));
byId({ id: "p1", price: 9 }, { id: "p1", price: 12 }); // true

date

date: Equality<Date> = dateEq

Equality for Date values. Compares by numeric time value.

See

Equality.number for numeric value equality.

Example

Equality.date(new Date("2024-01-01"), new Date("2024-01-01")); // true

number

number: Equality<number> = numberEq

Equality for numbers. Uses strict equality.

See

Equality.date for chronological timestamp equality.

Example

Equality.number(42, 42); // true

string

string: Equality<string> = stringEq

Equality for strings. Case-sensitive.

See

Equality.by to adapt equality checks to object properties.

Example

Equality.string("hello", "hello"); // true
Equality.string("hello", "Hello"); // false

struct

struct: <R>(fields) => Equality<R>

Derives deep equality for a record from field-level Equality checkers.

Type Parameters

R

R extends Record<string, unknown>

Parameters

fields

{ [K in string | number | symbol]: Equality<R[K]> }

Returns

Equality<R>

See

• Equality.tuple for positional tuple equality.
• Equality.by to compare single record fields.

Example

const userEq = Equality.struct({
  id: Equality.string,
  age: Equality.number,
});

tuple

tuple: <T>(…equalities) => Equality<T>

Derives element-wise equality for a tuple from positional Equality checkers.

Type Parameters

T

T extends readonly unknown[]

Parameters

equalities

…{ [K in string | number | symbol]: Equality<T[K]> }

Returns

Equality<T>

See

• Equality.struct for record structural equality.
• Equality.array for variable-length collection equality.

Example

const pairEq = Equality.tuple(Equality.string, Equality.number);
pairEq(["a", 1], ["a", 1]); // true