I'm learning now if conditions as well as tables, and I'm trying to get a table of the months, and using a select element to choose the month - as well as concealing days of months accordingly (for example selecting February would hide the boxes of days 30 and 31). It's not working and I would very much appreciate your help.

```
<label for="months-title">Month: </label>
        <select name="months" id="months">
            <option value="">--Select month--</option>
            <option value="january">January</option>
            <option value="february">February</option>
            <option value="march">March</option>
            <option value="april">April</option>
            <option value="may">May</option>
            <option value="june">June</option>
            <option value="july">July</option>
            <option value="august">August</option>
            <option value="september">September</option>
            <option value="october">October</option>
            <option value="november">November</option>
            <option value="december">December</option>
        </select>

        <table class="months-table">
            <tr>
                <td>1</td>
                <td>2</td>
                <td>3</td>
                <td>4</td>
            </tr>
            <tr>
                <td>5</td>
                <td>6</td>
                <td>7</td>
                <td>8</td>
            </tr>
            <tr>
                <td>9</td>
                <td>10</td>
                <td>11</td>
                <td>12</td>
            </tr>
            <tr>
                <td>13</td>
                <td>14</td>
                <td>15</td>
                <td>16</td>
            </tr>
            <tr>
                <td>17</td>
                <td>18</td>
                <td>19</td>
                <td>20</td>
            </tr>
            <tr>
                <td>21</td>
                <td>22</td>
                <td>23</td>
                <td>24</td>
            </tr>
            <tr>
                <td>25</td>
                <td>26</td>
                <td>27</td>
                <td>28</td>
            </tr>
            <tr class="last-month-tr">
                <td>29</td>
                <td class="thirtieth-month">30</td>
                <td class="thirty-1st-month">31</td>
            </tr>
        </table>

let monthsTable = document.querySelector('.months-table');
let monthsTitle = document.querySelector('.months-title');
let months = document.getElementById('months');
let lastMonthTr = document.querySelector('.last-month-tr');
let thirtyFirstMonth = document.querySelector('.thirty-1st-month');

months.onchange = function daysChange() {
    const selectedMonth = months.value;

    if (selectedMonth === 'April' || selectedMonth === 'June' || selectedMonth === 'September' || selectedMonth === 'November') {
        thirtyFirstMonth.style.visibility === 'hidden';
    } else if (selectedMonth === 'February') {
        lastMonthTr.style.visibility === 'hidden';
    }
}

```

I also understand my code is quite cumbersome and I might not be naming variables properly; would also appreciate tips for that.