Type Alias: ExtractField<T, K>

ExtractField<T, K>: T extends Record<K, infer U> ? U : never

ExtractField is a utility type that extracts the type of a specific field from a type T. This type takes two parameters:

• T, the type from which the field type is to be extracted.
• K, the key of the field to be extracted from T.

The utility type works as follows:

• T extends Record<K, infer U>: This conditional check verifies if T can be assigned to a record type with a key K and some value. If it can, TypeScript infers the type of this value and assigns it to U.

• U is returned when T is assignable to Record<K, infer U>, i.e., when T has the key K.

• If T does not have the key K, the utility type returns never.

This utility type is powerful as it allows the extraction of a specific field's type dynamically, given the field's name. It is useful when working with complex and dynamic types where the structure might not be known ahead of time.

Type Parameters

Defined in

lib/types.ts:174 (opens in a new tab)