if (true) {
    const name = 'john';
    let number = '123';
    var email = '[email protected]';
}

console.log(email, number, name);

for (var i = 0; i < 5; i++) {
    setTimeout(() => {
        console.log(i);
    })
}

const persons = [
    {
        name: 'John Doe',
        email: '[email protected]',
        salary: '100000',
    },
    {
        name: 'Jane Doe',
        email: '[email protected]',
        salary: '90000',
    },
];

const createSearch = () => {
    const cache = {};

    return (amount) => {
        if (!cache[amount]) {
            cache[amount] = contacts.filter(item => item.salary > amount);
        }

        return cache[amount];
    }
};

const Vehicle = function (color, wheelCount) {
    this.color = color;
    this.wheelCount = wheelCount;
};

Vehicle.prototype = {
    getColor: function () {
        return this.color;
    },

    getWheelCount: function () {
        return this.wheelCount;
    }
};

const Car = function (color) {
    Vehicle.call(this, color, 4);
};

Car.prototype = Object.assign({}, Vehicle.prototype);
Car.prototype.constructor = 'Car';

const car = new Car('red');

console.log(car instanceof Car);

fetch('//google.com')
    .then(function () {
        fetch('//yandex.ru')
    })
    .then(function () {
        fetch('//facebook.ru')
    })
    .then(() => {
        fetch('//twitter.ru')
    });

fetch('//google.com')
    .then(function () {
        throw new Error('some error');
    })
    .then(function () {
        fetch('//facebook.ru')
    })
    .then(() => {
        fetch('//twitter.ru')
    }).catch(() => {
        console.error('error occured');        
    }).then(() => {
        fetch('//yandex.ru');    
    });

fetch('https://google.com')
    .then((json) => {
        return json()
    })
    .then((data) => {
        return data
    })