src/app/shared/pipes/pair/pair.pipe.ts

/********************************************************************************
 * Copyright (c) 2020 Contributors to the Eclipse Foundation
 *
 * See the NOTICE file(s) distributed with this work for additional
 * information regarding copyright ownership.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0
 *
 * SPDX-License-Identifier: EPL-2.0
 ********************************************************************************/

import {Pipe, PipeTransform} from "@angular/core";

@Pipe({
    name: "pair"
})
export class PairPipe implements PipeTransform {

    /**
     * Transforms an array to an array of pair elements. For example, [0, 1, 2, 3] is transformed to [[0, 1], [2, 3]].
     * @param array Array to transform
     * @param pairSize Maximal size of each pair (default = 2)
     */
    public transform<T>(array: T[], pairSize: number = 2): T[][] {
        if (!Array.isArray(array)) {
            return [];
        }

        pairSize = Math.max(Math.round(pairSize), 1);

        const result: T[][] = [];

        for (let i = 0; i < array.length; i += pairSize) {
            const pair = Array(pairSize)
                .fill(0).map((_, index) => array[i + index])
                .filter((item) => item != null);

            if (pair.length > 0) {
                result.push(pair);
            }
        }

        return result;
    }

}