declare global {
    interface ReadonlyArray<T> {
        /**
         * Calls a defined callback function on each combination of elements from
         * two arrays to find matching pairs, and returns a new array containing
         * both unmatched and matched values.
         *
         * @param other - The other array to match (join) against.
         *
         * @param on - A function that accepts two arguments - the pair of elements
         *  from the two arrays. The function should return `true` if the
         *  pair of elements match (should join). The outerJoin method calls the
         *  function one time for each combination of elements from the two arrays.
         *
         * @returns An array of left and right pairs.
         */
        outerJoin<U>(other: ReadonlyArray<U>, on: (left: T, right: U) => boolean): Array<{
            left: T;
            right: U;
        } | {
            left: T;
            right: null;
        } | {
            left: null;
            right: U;
        }>;
    }
    interface Array<T> {
        /**
         * Calls a defined callback function on each combination of elements from
         * two arrays to find matching pairs, and returns a new array containing
         * both unmatched and matched values.
         *
         * @param other - The other array to match (join) against.
         *
         * @param on - A function that accepts two arguments - the pair of elements
         *  from the two arrays. The function should return `true` if the
         *  pair of elements match (should join). The outerJoin method calls the
         *  function one time for each combination of elements from the two arrays.
         *
         * @returns An array of left and right pairs.
         */
        outerJoin<U>(other: ReadonlyArray<U>, on: (left: T, right: U) => boolean): Array<{
            left: T;
            right: U;
        } | {
            left: T;
            right: null;
        } | {
            left: null;
            right: U;
        }>;
    }
}
export {};