Type alias Methods<T>

Methods<T>: {
    [K in Keys<T>]-?: ExcludeNullable<T[K]> extends AnyFunction
        ? K
        : never
}[Keys<T>]

Get the literal names of keys that are methods in object type T

Methods<{
     foo: () => void;
     bar: (a: any) => string;
     barBaz: string;
     bazBar: Numeric;
   }> // Result: 'foo' | 'bar'