Здравей, давам ти решенията на 2 и 3 задача. На първа нямам пълен брой точки.

Задача 2.

function solveClasses() {

    class Developer {

        constructor(firstName, lastName) {

            this.firstName = firstName;

            this.lastName = lastName;

            this.baseSalary = 1000;

            this.tasks = [];

            this.experience = 0;

        }

        addTask(id, taskName, priority) {

            if (priority === 'high') {

                this.tasks.unshift({ id, taskName, priority });

            }

            else {

                this.tasks.push({ id, taskName, priority });

            }

            return `Task id ${id}, with ${priority} priority, has been added.`;

        }

        doTask() {

            let task;

            let index = 0;

            for (let i = this.tasks.length; i > 0; i++) {

                if (this.tasks[i].priority === 'high') {

                    task = this.tasks[i];

                    break;

                }

            }

            index = this.tasks.indexOf(task);

            this.tasks = this.tasks.splice(index, 1);

            return `${task.taskName}, you have finished all your tasks. You can rest now.`;

        }

        getSalary() {

            return `${this.firstName} ${this.lastName} has a salary of: ${this.baseSalary}`;

        }

        reviewTasks() {

            let result = [];

            result.push('Tasks, that need to be completed:');

            for (let task of this.tasks) {

                result.push(`${task.id}: ${task.taskName} - ${task.priority}`);

            }

            return result.join('\n');

        }

    }

    class Junior extends Developer {

        constructor(firstName, lastName, bonus, experience) {

            super(firstName, lastName);

            this.baseSalary = this.baseSalary + bonus;

            this.tasks = [];

            this.experience = experience;

        }

        learn(years) {

            this.experience += Number(years);

        }

    }

    class Senior extends Developer {

        constructor(firstName, lastName, bonus, experience) {

            super(firstName, lastName);

            this.baseSalary = this.baseSalary + bonus;

            this.experience = Number(experience) + 5;

        }

        changeTaskPriority(taskId) {

            let task = this.tasks.find(x => x.id === taskId);

            let index = this.tasks.indexOf(task);

            this.tasks = this.tasks.splice(index, 1);

            if (task.priority === 'high') {

                task.priority = 'low';

                this.tasks.push(task);

            }

            else {

                task.priority = 'high';

                this.tasks.unshift(task);

            }

            return task;

        }

    }

    return {

        Developer,

        Junior,

        Senior

    }

}

Задача 3.

class Parking {

    constructor(capacity) {

        this.capacity = Number(capacity);

        this.vehicles = [];

    }

    addCar(carModel, carNumber) {

        if (this.capacity === this.vehicles.length) {

            throw new Error('Not enough parking space.');

        }

        this.vehicles.push({ carModel, carNumber, payed: false });

        return `The ${carModel}, with a registration number ${carNumber}, parked.`;

    }

    removeCar(carNumber) {

        let car = this.vehicles.find(x => x.carNumber === carNumber);

        if (!car) {

            throw new Error('The car, you\'re looking for, is not found.');

        }

        if (car.payed === false) {

            throw new Error(`${carNumber} needs to pay before leaving the parking lot.`);

        }

        let index = this.vehicles.indexOf(car);

        this.vehicles = this.vehicles.splice(index, 1);

        return `${carNumber} left the parking lot.`;

    }

    pay(carNumber) {

        let car = this.vehicles.find(x => x.carNumber === carNumber);

        if (!car) {

            throw new Error(`${carNumber} is not in the parking lot.`);

        }

        if (car.payed === true) {

            throw new Error(`${carNumber}'s driver has already payed his ticket.`);

        }

        car.payed = true;

        return `${carNumber}'s driver successfully payed for his stay.`;

    }

    getStatistics(carNumber) {

        if (carNumber !== undefined) {

            let car = this.vehicles.find(x => x.carNumber === carNumber);

            return `${car.carModel} == ${car.carNumber} - ${car.payed === true ? 'Has payed' : 'Not payed'}`;

        }

        let result = [];

        let count = 0;

        for (let i = 0; i < this.vehicles.length; i++) {

            count++;

        }

        result.push(`The Parking Lot has ${this.capacity - count} empty spots left.`);

        let sorted = this.vehicles.sort((a, b) => a.carModel.localeCompare(b.carModel));

        for (let car of sorted) {

            result.push(`${car.carModel} == ${car.carNumber} - ${car.payed === true ? 'Has payed' : 'Not payed'}`);

        }

        return result.join('\n');

    }

}