extend.mjs

/**
 * Copyright schukai GmbH and contributors 2022. All Rights Reserved.
 * Node module: @schukai/monster
 * This file is licensed under the AGPLv3 License.
 * License text available at https://www.gnu.org/licenses/agpl-3.0.en.html
 */

import {isArray, isObject} from "../types/is.mjs";
import {typeOf} from "../types/typeof.mjs";

export {extend}

/**
 * Extend copies all enumerable own properties from one or
 * more source objects to a target object. It returns the modified target object.
 *
 * @param {object} target
 * @param {object}
 * @return {object}
 * @license AGPLv3
 * @since 1.10.0
 * @copyright schukai GmbH
 * @memberOf Monster.Data
 * @throws {Error} unsupported argument
 * @throws {Error} type mismatch
 */
function extend() {
    let o, i;

    for (i = 0; i < arguments.length; i++) {
        let a = arguments[i];

        if (!(isObject(a) || isArray(a))) {
            throw new Error('unsupported argument ' + JSON.stringify(a));
        }

        if (o === undefined) {
            o = a;
            continue;
        }

        for (let k in a) {

            let v = a?.[k];

            if (v === o?.[k]) {
                continue;
            }

            if ((isObject(v)&&typeOf(v)==='object') || isArray(v)) {

                if (o[k] === undefined) {
                    if (isArray(v)) {
                        o[k] = [];
                    } else {
                        o[k] = {};
                    }
                } else {
                    if (typeOf(o[k]) !== typeOf(v)) {
                        throw new Error("type mismatch: " + JSON.stringify(o[k]) + "(" + typeOf(o[k]) + ") != " + JSON.stringify(v) + "(" + typeOf(v) + ")");
                    }
                }

                o[k] = extend(o[k], v);

            } else {
                o[k] = v;
            }

        }
    }

    return o;
}