DeepCopy in TypeScript

util.service.ts

import { Injectable } from "@angular/core";

/**
 * Created by Joao Araujo (jocafi) on November 2018
 *
 * UtilService implements some util methods which can be used along the App development.
 *
 */
@Injectable()
export class UtilService {

    /**
     * Returns a deep copy of a object. It replaces the command JSON.parse(JSON.stringify(object)).
     *
     * <p>Best performance ran at https://jsperf.com/deep-copy-vs-json-stringify-json-parse/51
     *
     * @param obj Object to be copied.
     * @returns {any} Copy of object.
     */
    deepCopyObject(object) {
        let r, i, l;
        if (typeof object !== "object") {
            return object;
        }
        if (!object) {
            return object;
        }
        if (object.constructor === Array) {
            r = [];
            l = object.length;
            for (i = 0; i < l; i++) {
                r[i] = this.deepCopyObject(object[i]);
            }
            return r;
        }
        r = {};
        for (i of object) {
            r[i] = this.deepCopyObject(object[i]);
        }
        return r;
    }

    // alternative found at
    // https://dev.to/ptasker/best-way-to-copy-an-object-in-javascript-827
    deepCopy(obj) {
        if (typeof obj === "object") {
            return Object.keys(obj)
                .map(k => ({ [k]: this.deepCopy(obj[k]) }))
                .reduce((a, c) => Object.assign(a, c), {});
        } else if (Array.isArray(obj)) {
            return obj.map(this.deepCopy)
        }
        return obj;
    }

    deepCopyObjectInto(source, dest) {
        const sourceCopy = this.deepCopy(source);

        if (typeof sourceCopy !== "object" || sourceCopy == null) {
            throw new Error("Only objects can be copied. The source object has type of '" + (typeof source) + "'.");
        }

        if (typeof dest !== "object" || dest == null) {
            throw new Error("Only objects can be copied. The destination object has type of '" + (typeof dest) + "'.");
        }

        Object.keys(sourceCopy)
            .map(k => {
                dest[k] = this.deepCopy(sourceCopy[k]);
            });
    }

}