Javascript classList.remove 无法正常工作

Question

检查这个 fiddle :JSFiddle

HTML:

<table class="myTable">
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class=" someStyle">1</span>/<span class="otherStyle">15</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class=" someStyle">2</span>/<span class="otherStyle">16</span>
    </td>
  </tr>
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class="">3</span>/<span class="">17</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class="otherStyle">4</span>/<span class=" someStyle">18</span>
    </td>
  </tr>
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class="otherStyle">5</span>/<span class=" someStyle">19</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class="">6</span>/<span class="">20</span>
    </td>
  </tr>
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class="">7</span>/<span class="">21</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class=" someStyle">8</span>/<span class="otherStyle">22</span>
    </td>
  </tr>
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class="">9</span>/<span class="">23</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class="otherStyle">10</span>/<span class=" someStyle">24</span>
    </td>
  </tr>
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class="otherStyle">11</span>/<span class=" someStyle">25</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class="otherStyle">12</span>/<span class=" someStyle">26</span>
    </td>
  </tr>
  <tr>
    <th>Some text</th>
    <td class="align">
      <span class=" someStyle">13</span>/<span class="otherStyle">27</span>
    </td>
    <th>Some text</th>
    <td class="align">
      <span class=" someStyle">14</span>/<span class="otherStyle">28</span>
    </td>
  </tr>
</table>

JavaScript:

var myTbl = document.getElementsByClassName("myTable")[0];

var tSomeStyleClasses = myTbl.getElementsByClassName("someStyle");
console.log(tSomeStyleClasses);
for (i=0;i<tSomeStyleClasses.length;i++) {
    console.log(tSomeStyleClasses[i].classList);
    //tSomeStyleClasses[i].classList.remove("someStyle");
}

var tOtherStyleClasses = myTbl.getElementsByClassName("otherStyle");
console.log(tOtherStyleClasses);
for (i=0;i<tOtherStyleClasses.length;i++) {
    console.log(tOtherStyleClasses[i].classList);
    //tOtherStyleClasses[i].classList.remove("otherStyle");
}

并检查控制台日志。每个有 10 个条目，someStyle 和 otherStyle。现在取消注释 //tSomeStyleClasses[i].classList.remove("someStyle"); 和 //tOtherStyleClasses[i].classList.remove("otherStyle"); 和运行 fiddle 。再次检查控制台日志。应该删除 2 x 10 个样式，但它只删除了 5 个样式。 我想知道为什么？

Answer 1

.getElementsByClassName() 返回的值是一个事件 NodeList。它是“实时的”意味着当您更改列表中的元素时，列表本身会自动更新。因此，当您删除 用于查找元素的类时，列表会变短。因为您正在使用数字索引进行迭代，所以您最终会跳过元素。

处理这个问题的一个好方法是使用一个简单的 while 循环，只对列表的第一个元素进行操作，直到列表为空:

var tSomeStyleClasses = myTbl.getElementsByClassName("someStyle");

while (tSomeStyleClasses.length) {
    tSomeStyleClasses[0].classList.remove("someStyle");
}