javascript implementation of queue with extended functionality

queue.js

/* 
 * The MIT License
 *
 * Copyright 2022 denis.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

// source https://www.geeksforgeeks.org/implementation-queue-javascript/

/**
 * 
 * @type class
 */
class Queue
{
    /**
     * 
     * @returns {Queue}
     */
    constructor()
    {
        this.items = [];
    }

    /**
     * adding element to the queue
     * 
     * @param {type} element
     * @returns {undefined}
     */
    push(element)
    {
        this.items.push(element);
    }

    /**
     * removing element from the queue
     * returns underflow when called 
     * on empty queue
     * 
     * @returns {Object|undefined|String}
     */
    pop()
    {
        if (this.isEmpty()) {
            return "Underflow";
        }
        return this.items.shift();
    }

    /**
     * returns the Front element of 
     * the queue without removing it.
     *
     * @returns {Array|String}
     */
    front()
    {
        if (this.isEmpty()) {
            return "No elements in Queue";
        }
        return this.items[0];
    }

    /**
     * returns the Back element of 
     * the queue without removing it.
     *
     * @returns {Array|String}
     */
    back()
    {
        if (this.isEmpty()) {
            return "No elements in Queue";
        }
        return this.items[this.items.length - 1];
    }

    /**
     * return true if the queue is empty.
     * 
     * @returns {Boolean}
     */
    isEmpty()
    {
        return this.items.length === 0;
    }

    /**
     * 
     * @param {Function} func
     * @returns {undefined}
     */
    forEach(func) {
        for (let i = 0; i < this.items.length; i++) {
            func(i, this.items[i]);
        }
    }

    printQueue()
    {
        var str = "";
        for (var i = 0; i < this.items.length; i++) {
            str += this.items[i] + " ";
        }
        return str;
    }
}