ix/iterable/operators/groupjoin.mjs

The Interactive Extensions for JavaScript

import { IterableX } from '../iterablex.mjs';
import { createGrouping } from './_grouping.mjs';
import { empty } from '../empty.mjs';
import { identity } from '../../util/identity.mjs';
/** @ignore */
export class GroupJoinIterable extends IterableX {
    constructor(outer, inner, outerSelector, innerSelector, resultSelector) {
        super();
        this._outer = outer;
        this._inner = inner;
        this._outerSelector = outerSelector;
        this._innerSelector = innerSelector;
        this._resultSelector = resultSelector;
    }
    *[Symbol.iterator]() {
        const map = createGrouping(this._inner, this._innerSelector, identity);
        for (const outerElement of this._outer) {
            const outerKey = this._outerSelector(outerElement);
            const innerElements = map.has(outerKey) ? map.get(outerKey) : empty();
            yield this._resultSelector(outerElement, innerElements);
        }
    }
}
/**
 * Correlates the elements of two iterable sequences based on equality of keys and groups the results.
 *
 * @template TOuter The type of the elements of the first iterable sequence.
 * @template TInner The type of the elements of the second iterable sequence.
 * @template TKey The type of the keys returned by the key selector functions.
 * @template TResult The type of the result elements.
 * @param {Iterable<TInner>} inner The async-enumerable sequence to join to the first sequence.
 * @param {((value: TOuter) => TKey)} outerSelector A function to extract the join key from each
 * element of the first sequence.
 * @param {((value: TInner) => TKey)} innerSelector A function to extract the join key from each
 * element of the second sequence.
 * @param {((outer: TOuter, inner: Iterable<TInner>) => TResult)} resultSelector A function to create a result
 * element from an element from the first sequence and a collection of matching elements from the second sequence.
 * @returns {OperatorFunction<TOuter, TResult>} An operator that returns an iterable sequence that contains the result elements
 * that are obtained by performing a grouped join on two sequences.
 */
export function groupJoin(inner, outerSelector, innerSelector, resultSelector) {
    return function groupJoinOperatorFunction(outer) {
        return new GroupJoinIterable(outer, inner, outerSelector, innerSelector, resultSelector);
    };
}

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