deepDiscriminate

The deepDiscriminate() method discriminates an object by the value of a deep property (type guard for unions).

Interactive example

Syntax

Classic signature

function deepDiscriminate<
	GenericInput extends object,
	GenericObjectProjection extends ObjectProjection<GenericInput>,
	GenericPath extends keyof GenericObjectProjection,
	GenericInput extends EligibleEqual
>(
	input: GenericInput,
	path: GenericPath,
	value: (MaybeArray<(GenericInput & GenericObjectProjection[GenericPath])> | MaybeArray<GenericObjectProjection[GenericPath]>)
): input is Extract<GenericInput, UnFlatObject<{
	[Prop in GenericPath]: GenericInput;
}>>

Curried signature

function deepDiscriminate<
	GenericInput extends object,
	GenericObjectProjection extends ObjectProjection<GenericInput>,
	GenericPath extends keyof GenericObjectProjection,
	GenericInput extends EligibleEqual
>(
	path: GenericPath,
	value: ...
): (input: GenericInput) => input is Extract<GenericInput, UnFlatObject<{
	[Prop in GenericPath]: GenericInput;
}>>

Parameters

• input: The object to discriminate (often a union type).
• path: The path to the discriminant property (e.g. "user.role").
• input: The expected value (or array of values) for discrimination.

Return value

A boolean that acts as a type guard to narrow the union type.

See also

• discriminate - Discriminates by a top-level property
• getDeepProperty - Retrieves a deep property