How to make a Bootstrap dropdown show up in front of sticky table headers?

I followed a CSS Tricks tutorial to get a table with a sticky header and first column, and tried adding a Bootstrap dropdown inside of the first column.

Problem is, the dropdown shows up in front of the parent cell but behind all of the others of the first column:

I've tried changing the position of the cell to relative, switching the z-index of the dropdown menu to a higher value but the dropdown is still behind the first column.

Here's a JSFiddle with a minimum, reproducible example: https://jsfiddle.net/maxencelav/hwsrcmL6/14/

@import url("https://fonts.googleapis.com/css2?family=Fraunces:ital,wght@0,700;1,200&display=swap");
table {
  font-family: "Fraunces", serif;
  font-size: 125%;
  white-space: nowrap;
  margin: 3px;
  border: none;
  border-collapse: separate;
  border-spacing: 0;
  table-layout: fixed;
  border: 1px solid black;
}

table td,
table th {
  border: 1px solid black;
  padding: 0.5rem 1rem;
}

table thead th {
  padding: 3px;
  position: sticky;
  top: 0;
  z-index: 1;
  width: 25vw;
  background: white;
}

table td {
  background: #fff;
  padding: 4px 5px;
  text-align: center;
}

table tbody th {
  font-weight: 100;
  font-style: italic;
  text-align: left;
  position: relative;
}

table thead th:first-child {
  position: sticky;
  left: 0;
  z-index: 2;
}

table tbody th {
  position: sticky;
  left: 0;
  background: white;
  z-index: 1;
}

caption {
  text-align: left;
  padding: 0.25rem;
  position: sticky;
  left: 0;
}

[role="region"][aria-labelledby][tabindex] {
  width: 100%;
  max-height: 98vh;
  overflow: auto;
}

#team-cell-container {
  display: grid;
  grid-template-columns: 1fr auto;
  align-items: center;
  margin: 0;
  gap: 5px;
}

<script src="https://code.jquery.com/jquery-3.4.1.slim.js"></script>
<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/css/bootstrap.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.16.0/umd/popper.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.4.1/js/bootstrap.js"></script>
<link href="https://stackpath.bootstrapcdn.com/font-awesome/4.7.0/css/font-awesome.css" rel="stylesheet" />


<!-- Based off https://css-tricks.com/a-table-with-both-a-sticky-header-and-a-sticky-first-column/ -->

<table>
  <thead>
    <tr>
      <th>Teams</th>
      <th>1</th>
      <th>2</th>
      <th>3</th>
      <th>4</th>
      <th>5</th>
      <th>6</th>
      <th>7</th>
      <th>8</th>
      <th>9</th>
      <th>Runs</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>
        <div id="team-cell-container">
          Milwaukee Brewers
          <div class="dropdown">
            <i class="fa fa-cog" type="button" id="dropdown-item" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"></i>
            <div class="dropdown-menu" aria-labelledby="dropdown-item">
              <a class="dropdown-item" href="#">Action</a>
              <a class="dropdown-item" href="#">Another action</a>
              <a class="dropdown-item" href="#">Something else here</a>
            </div>
          </div>
        </div>
      </th>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>1</td>
      <td>1</td>
      <td>0</td>
      <td>1</td>
      <td>13</td>
    </tr>
    <tr>
      <th>Los Angles Dodgers</th>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>2</td>
      <td>3</td>
      <td>20</td>
    </tr>
    <tr>
      <th>New York Mets</th>
      <td>0</td>
      <td>1</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>2</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>12</td>
    </tr>
    <tr>
      <th>St. Louis Cardinals</th>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>3</td>
      <td>2</td>
      <td>3</td>
      <td>25</td>
    </tr>
  </tbody>
</table>

Solution

This is problem with CSS position and z-index. It was explained by this question. (Or see my testing).

To make position: absolute with high z-index appears on top of other relative, you have to set z-index of the others to be lower than z-index of the parent dropdown . This confirmed work by this answer.

First, add some identity to your table.

<!-- Based off https://css-tricks.com/a-table-with-both-a-sticky-header-and-a-sticky-first-column/ -->

<table id="my-table">
  <thead>
    <tr>
      <th>Teams</th>
      <th>1</th>
      <th>2</th>
      <th>3</th>
      <th>4</th>
      <th>5</th>
      <th>6</th>
      <th>7</th>
      <th>8</th>
      <th>9</th>
      <th>Runs</th>
    </tr>
  </thead>
  <tbody>
    <tr>
      <th>
        <div id="team-cell-container">
          Milwaukee Brewers
          <div class="dropdown">
            <i class="fa fa-cog" type="button" id="dropdown-item" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"></i>
            <div class="dropdown-menu" aria-labelledby="dropdown-item">
              <a class="dropdown-item" href="#">Action</a>
              <a class="dropdown-item" href="#">Another action</a>
              <a class="dropdown-item" href="#">Something else here</a>
            </div>
          </div>
        </div>
      </th>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>1</td>
      <td>1</td>
      <td>0</td>
      <td>1</td>
      <td>13</td>
    </tr>
    <tr>
      <th>Los Angles Dodgers</th>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>2</td>
      <td>3</td>
      <td>20</td>
    </tr>
    <tr>
      <th>New York Mets</th>
      <td>0</td>
      <td>1</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>2</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>12</td>
    </tr>
    <tr>
      <th>St. Louis Cardinals</th>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>3</td>
      <td>2</td>
      <td>4</td>
      <td>3</td>
      <td>2</td>
      <td>3</td>
      <td>25</td>
    </tr>
    <tr>
      <th>Houston Astros</th>
      <td>3</td>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>2</td>
      <td>3</td>
      <td>1</td>
      <td>3</td>
      <td>1</td>
      <td>20</td>
    </tr>
    <tr>
      <th>Toronto Blue Jays</th>
      <td>2</td>
      <td>4</td>
      <td>4</td>
      <td>1</td>
      <td>1</td>
      <td>2</td>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>22</td>
    </tr>
    <tr>
      <th>Boston Red Sox</th>
      <td>4</td>
      <td>4</td>
      <td>4</td>
      <td>0</td>
      <td>3</td>
      <td>0</td>
      <td>0</td>
      <td>1</td>
      <td>1</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Chicago Cubs</th>
      <td>1</td>
      <td>1</td>
      <td>0</td>
      <td>0</td>
      <td>2</td>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>12</td>
    </tr>
    <tr>
      <th>Philadelphia Phillies</th>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>1</td>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Chicago White Sox</th>
      <td>2</td>
      <td>0</td>
      <td>2</td>
      <td>3</td>
      <td>4</td>
      <td>2</td>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>19</td>
    </tr>
    <tr>
      <th>San Diego Padres</th>
      <td>2</td>
      <td>2</td>
      <td>3</td>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>2</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Cleveland Indians</th>
      <td>1</td>
      <td>0</td>
      <td>0</td>
      <td>3</td>
      <td>2</td>
      <td>1</td>
      <td>3</td>
      <td>1</td>
      <td>0</td>
      <td>11</td>
    </tr>
    <tr>
      <th>San Francisco Giants</th>
      <td>1</td>
      <td>3</td>
      <td>1</td>
      <td>4</td>
      <td>1</td>
      <td>1</td>
      <td>1</td>
      <td>2</td>
      <td>3</td>
      <td>17</td>
    </tr>
    <tr>
      <th>Cincinatti Reds</th>
      <td>2</td>
      <td>2</td>
      <td>4</td>
      <td>1</td>
      <td>4</td>
      <td>2</td>
      <td>2</td>
      <td>3</td>
      <td>3</td>
      <td>23</td>
    </tr>
    <tr>
      <th>Minnesota Twins</th>
      <td>4</td>
      <td>4</td>
      <td>1</td>
      <td>0</td>
      <td>2</td>
      <td>0</td>
      <td>3</td>
      <td>1</td>
      <td>3</td>
      <td>18</td>
    </tr>
    <tr>
      <th>Tampa Bay Rays</th>
      <td>4</td>
      <td>1</td>
      <td>3</td>
      <td>0</td>
      <td>2</td>
      <td>1</td>
      <td>4</td>
      <td>0</td>
      <td>1</td>
      <td>16</td>
    </tr>
    <tr>
      <th>Miami Marlins</th>
      <td>0</td>
      <td>3</td>
      <td>0</td>
      <td>4</td>
      <td>3</td>
      <td>3</td>
      <td>0</td>
      <td>1</td>
      <td>4</td>
      <td>18</td>
    </tr>
    <tr>
      <th>Oakland Athletics</th>
      <td>3</td>
      <td>3</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>2</td>
      <td>0</td>
      <td>1</td>
      <td>0</td>
      <td>15</td>
    </tr>
    <tr>
      <th>Detroit Tigers</th>
      <td>3</td>
      <td>4</td>
      <td>1</td>
      <td>2</td>
      <td>3</td>
      <td>2</td>
      <td>0</td>
      <td>0</td>
      <td>4</td>
      <td>19</td>
    </tr>
    <tr>
      <th>Pittsburgh Pirates</th>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>3</td>
      <td>0</td>
      <td>2</td>
      <td>2</td>
      <td>2</td>
      <td>2</td>
      <td>15</td>
    </tr>
    <tr>
      <th>Seattle Mariners</th>
      <td>1</td>
      <td>3</td>
      <td>3</td>
      <td>1</td>
      <td>2</td>
      <td>2</td>
      <td>0</td>
      <td>4</td>
      <td>0</td>
      <td>16</td>
    </tr>
    <tr>
      <th>Atlanta Braves</th>
      <td>4</td>
      <td>3</td>
      <td>0</td>
      <td>3</td>
      <td>4</td>
      <td>4</td>
      <td>4</td>
      <td>4</td>
      <td>3</td>
      <td>29</td>
    </tr>
  </tbody>
</table>
</div>

Then use Bootstrap dropdown events to listen on show or hide the dropdown element.

$('#my-table .dropdown').on('show.bs.dropdown', (event) => {
    let thisTable = event.target.closest('table');
    thisTable.classList.add('dropdowns-opened');
    // add class to all <tr>
    $(thisTable).find('tr').addClass('non-dropdown');
    // remove class of this <tr>
    event.target.closest('tr').classList.remove('non-dropdown');
});

$('#my-table .dropdown').on('hidden.bs.dropdown', (event) => {
    let thisTable = event.target.closest('table');
    thisTable.classList.remove('dropdowns-opened');
    $(thisTable).find('tr').removeClass('non-dropdown');
});

The JavaScript above will add and remove class when dropdown element show or hide.

Now, add some CSS class to make dropdown appears on top of other.

table.dropdowns-opened tbody tr.non-dropdown th {
    z-index: 0;
}

See it in action on JsFiddle.

You maybe change your current z-index: 1 to 2 and use the class above from z-index: 0 to 1 if the sticky functional is not work as expected.