如何解决 css 中的嵌套选择器？

Question

table的padding应该是8px，但是当有modal的时候，padding应该是0，这样才能填满整个cell，见图

如何解决嵌套在 table 和不同种类的 class 和 id 下的特定选择器？

我尝试过组合：#tabletu .modal #myBtn2 td 但都没有使填充消失。例如：

// Get the modal
var modal = document.getElementById("myModal");

// Get the button that opens the modal
var btn = document.getElementById("myBtn2");

// Get the <span> element that closes the modal
var span = document.getElementsByClassName("close")[0];

// When the user clicks the button, open the modal 
btn.onclick = function() {
  modal.style.display = "block";
}

// When the user clicks on <span> (x), close the modal
span.onclick = function() {
  modal.style.display = "none";
}

// When the user clicks anywhere outside of the modal, close it
window.onclick = function(event) {
  if (event.target == modal) {
    modal.style.display = "none";
  }
}

#tabletu .modal {
  padding: 0px;
}

#tabletu {
  background-color: transparent;
  border-collapse: collapse;
  width: 100%;
}

#tabletu td,
th {
  border: 1px solid #000000;
  padding: 8px;
}

#tabletu th {
  padding: 8px;
  text-align: left;
  border: 1px solid #000000;
  background-color: rgba(0, 110, 167, 1);
  color: white;
}


/* The Modal (background) */

.modal {
  display: none;
  /* Hidden by default */
  position: fixed;
  /* Stay in place */
  z-index: 1;
  /* Sit on top */
  padding-top: 100px;
  /* Location of the box */
  left: 0;
  top: 0;
  width: 100%;
  /* Full width */
  height: 100%;
  /* Full height */
  overflow: auto;
  /* Enable scroll if needed */
  background-color: rgb(0, 0, 0);
  /* Fallback color */
  background-color: rgba(0, 0, 0, 0.4);
  /* Black w/ opacity */
}


/* Modal Content */

.modal-content {
  background-color: #fefefe;
  margin: auto;
  padding: 20px;
  border: 1px solid #888;
  width: 80%;
}

.modal td {
  padding: 0px;
}


/* The Close Button */

.close {
  color: #aaaaaa;
  float: right;
  font-size: 28px;
  font-weight: bold;
}

.close:hover,
.close:focus {
  color: #000;
  text-decoration: none;
  cursor: pointer;
}

.notebook {
  border-collapse: collapse;
  width: 70%;
}

.notebook td:hover {
  background-color: #ddd;
}

.notebook td,
.notebook th {
  border: 1px solid #ddd;
  padding: 0px;
}

.block {
  display: block;
  width: 100%;
  border: none;
  background-color: rgba(0, 166, 214, 1);
  padding: 14px 28px;
  font-size: 16px;
  cursor: pointer;
  text-align: center;
  box-sizing: border-box;
}

.block:hover {
  background-color: rgba(0, 166, 214, 0.78);
  color: black;
}

.month {
  text-align: center;
}

#category {
  padding: 8px;
}

<h2>Experiment Notebook</h2>
<center>
  <table id="tabletu" class="notebook">
    <tr id="category">
      <th></th>
      <th id="category">Test1</th>
      <th>Test2</th>
      <th>Other</th>
    </tr>
    <tr>
      <td rowspan=2 class="month">April</td>
      <td>
        <!-- Trigger/Open The Modal -->
        <button id="myBtn2" class="block">Open Modal</button>

        <!-- The Modal -->
        <div id="myModal" class="modal">

          <!-- Modal content -->
          <div class="modal-content">
            <span class="close">&times;</span>
            <p>Some text in the Modal..</p>
          </div>

        </div>
      </td>
      <td><button id="myBtn2" class="block">Open Modal</button></td>
      <td>Germany</td>
    </tr>
    <tr>

      <td>Berglunds snabbköp</td>
      <td>Christina Berglund</td>
      <td>Sweden</td>
    </tr>
    <tr>
      <td></td>
      <td>Centro comercial Moctezuma</td>
      <td>Francisco Chang</td>
      <td>Mexico</td>
    </tr>
    <tr>
      <td></td>
      <td>Ernst Handel</td>
      <td>Roland Mendel</td>
      <td>Austria</td>
    </tr>
    <tr>
      <td></td>
      <td>Island Trading</td>
      <td>Helen Bennett</td>
      <td>UK</td>
    </tr>
    <tr>
      <td></td>
      <td>Königlich Essen</td>
      <td>Philip Cramer</td>
      <td>Germany</td>
    </tr>
    <tr>
      <td></td>
      <td>Laughing Bacchus Winecellars</td>
      <td>Yoshi Tannamuri</td>
      <td>Canada</td>
    </tr>
    <tr>
      <td></td>
      <td>Magazzini Alimentari Riuniti</td>
      <td>Giovanni Rovelli</td>
      <td>Italy</td>
    </tr>
    <tr>
      <td></td>
      <td>North/South</td>
      <td>Simon Crowther</td>
      <td>UK</td>
    </tr>
    <tr>
      <td></td>
      <td>Paris spécialités</td>
      <td>Marie Bertrand</td>
      <td>France</td>
    </tr>
  </table>

</center>

在 A. Meshu 的帮助下，我到目前为止已经完成了，但模态框下方仍然有一条细小的白线。

Answer 1

当我们点击模式打开时，让我们在单元格中添加一个modal-open class。 modal-open class 有 css 应用 0px 填充。当我们关闭模式时，删除 class 并因此删除填充。

        #tabletu {
            background-color: transparent;
            border-collapse: collapse;
            width:100%;
        }

        #tabletu td, th {
            border: 1px solid #000000;
            padding: 8px;
        }

        #tabletu th {
            padding: 8px;
            text-align: left;
            border: 1px solid #000000;  
            background-color: rgba(0,110,167,1);
            color: white;
        }
        /* The Modal (background) */
        .modal {
            display: none; /* Hidden by default */
            position: fixed; /* Stay in place */
            z-index: 1; /* Sit on top */
            padding-top: 100px; /* Location of the box */
            left: 0;
            top: 0;
            width: 100%; /* Full width */
            height: 100%; /* Full height */
            overflow: auto; /* Enable scroll if needed */
            background-color: rgb(0,0,0); /* Fallback color */
            background-color: rgba(0,0,0,0.4); /* Black w/ opacity */
        }

        .btn-cell {
          padding: 8px;
        }
        .btn-cell.modal-open {
          padding: 0px!important;
        }
        /* Modal Content */
        .modal-content {
            background-color: #fefefe;
            margin: auto;
            padding: 20px;
            border: 1px solid #888;
            width: 80%;
        }


        .modal td {
            padding:0px;
        }
        /* The Close Button */
        .close {
            color: #aaaaaa;
            float: right;
            font-size: 28px;
            font-weight: bold;
        }

        .close:hover,
        .close:focus {
            color: #000;
            text-decoration: none;
            cursor: pointer;
        }

        .notebook {  
            border-collapse: collapse;
            width:70%;}
        .notebook td:hover {background-color: #ddd;}
        .notebook td, .notebook th {
            border: 1px solid #ddd;
            padding: 0px;
        }
        .block {
            display: block;
            width: 100%;
            border: none;
            background-color: rgba(0, 166, 214, 1);
            padding: 14px 28px;
            font-size: 16px;
            cursor: pointer;
            text-align: center;
            box-sizing: border-box;
        }

        .block:hover {
            background-color: rgba(0, 166, 214, 0.78);
            color: black;
        }
        .month {
            text-align: center;
        }        
        #category {
            padding:8px;
        }
    </style>
</head>
<body>

    <h2>Experiment Notebook</h2>
    <center>
        <table id="tabletu" class="notebook">
            <tr id="category">
                <th ></th>
                <th id="category">Test1</th>
                <th>Test2</th>
                <th>Other</th>
            </tr>
            <tr>
                <td rowspan=2 class="month">April</td>
                <td class='btn-cell'><!-- Trigger/Open The Modal -->
                    <button id="myBtn2" class="block ">Open Modal</button>

                    <!-- The Modal -->
                    <div id="myModal" class="modal">

                        <!-- Modal content -->
                        <div class="modal-content">
                            <span class="close">&times;</span>
                            <p>Some text in the Modal..</p>
                        </div>

                    </div>
                </td>
                <td class='btn-cell'><button id="myBtn2" class="block ">Open Modal</button></td>
                <td>Germany</td>
            </tr>
            <tr>

                <td>Berglunds snabbköp</td>
                <td>Christina Berglund</td>
                <td>Sweden</td>
            </tr>
            <tr>
                <td></td>
                <td>Centro comercial Moctezuma</td>
                <td>Francisco Chang</td>
                <td>Mexico</td>
            </tr>
            <tr>
                <td></td>
                <td>Ernst Handel</td>
                <td>Roland Mendel</td>
                <td>Austria</td>
            </tr>
            <tr>
                <td></td>
                <td>Island Trading</td>
                <td>Helen Bennett</td>
                <td>UK</td>
            </tr>
            <tr>
                <td></td>
                <td>Königlich Essen</td>
                <td>Philip Cramer</td>
                <td>Germany</td>
            </tr>
            <tr>
                <td></td>
                <td>Laughing Bacchus Winecellars</td>
                <td>Yoshi Tannamuri</td>
                <td>Canada</td>
            </tr>
            <tr>
                <td></td>
                <td>Magazzini Alimentari Riuniti</td>
                <td>Giovanni Rovelli</td>
                <td>Italy</td>
            </tr>
            <tr>
                <td></td>
                <td>North/South</td>
                <td>Simon Crowther</td>
                <td>UK</td>
            </tr>
            <tr>
                <td></td>
                <td>Paris spécialités</td>
                <td>Marie Bertrand</td>
                <td>France</td>
            </tr>
        </table>

    </center>



    <script>
        // Get the modal
        var modal = document.getElementById("myModal");

        // Get the button that opens the modal
        var btn = document.getElementById("myBtn2");

        // Get the <span> element that closes the modal
        var span = document.getElementsByClassName("close")[0];

        // When the user clicks the button, open the modal 
        btn.onclick = function() {
            modal.style.display = "block";
            togglePadding(true)
        }

        // When the user clicks on <span> (x), close the modal
        span.onclick = function() {
            modal.style.display = "none";
            togglePadding()
        }

        // When the user clicks anywhere outside of the modal, close it
        window.onclick = function(event) {
            if (event.target == modal) {
                modal.style.display = "none";
                togglePadding()
            }
        }

        var togglePadding = function(add) {
          var buttonCells = document.getElementsByClassName('btn-cell')
            for (var i = 0; i < buttonCells.length; i++) {
              if (add) {
                buttonCells[i].classList.add('modal-open')
              }
              else {
                buttonCells[i].classList.remove('modal-open')
              }
            }
        }

    </script>

Answer 2

因为你在父 #tabletu td 上有 id 选择器，所以它克服了 class 选择器 .modal td。您只需要使用 !important 来克服 id 选择器：

.modal td {padding:0} !important

Answer 3

您可以通过向包含 button 的所有 <td> 添加一个 class 来解决它，然后用 !important 设置样式。在这个例子中我使用了 modalTD class:

.modalTD {padding: 0!important;} // remove horizontal padding
.modalTD button {height: 65px!important;} // make the button height wrap the entire cell

html 看起来像这样：

.
.
.
<td class="modalTD"><!-- Trigger/Open The Modal -->
  <button id="myBtn2" class="block">Open Modal</button>
.
.
.

附带说明：总有一天 :has pseudo-class 会让我们的生活更轻松，但现在它不支持任何东西......

编辑

另一个解决方案会更有效率，但它会影响整行（我必须说不是那么糟糕），您可以尝试的是：

#tabletu tr:nth-of-type(2) td {padding: 0;}

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