Type Alias ListLikeIndex<L>

ListLikeIndex: L extends readonly any[]
    ? number
    : L extends ReadonlyMap<infer K, any>
        ? K
        : L extends Map<infer K, any>
            ? K
            : L extends Record<infer K, any>
                ? K
                : L extends Set<any>
                | ReadonlySet<any>
                | Iterable<any>
                    ? never
                    : string | number

Extract the key or index type from a keyed list-like structure.

Type Parameters

L
List-like type

Remarks

For arrays and other non-keyed collections, this defaults to string | number. If the structure is not keyed, the type resolves to never.

Example

type I1 = ListLikeIndex< Record< string, number > >;  // string
type I2 = ListLikeIndex< Map< number, string > >;     // number
type I3 = ListLikeIndex< number[] >;                  // number

Type Alias ListLikeIndex<L>

Type Parameters

Remarks

Example

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