javascript - 更改多个子元素的 HTML(这个 jquery 选择器的 JS 版本是什么？)

Question

我正在通过我的代码在需要的地方用 JS 替换 jQuery，在某些情况下我需要清除和重建一些表数据，为此我按以下方式使用 jQuery:

$("[id*='mg_row_document'] td:nth-of-type(2)").html('');

我能够为纯 JS 组合起来的就是这个，但是不起作用，我只获得元素的 NodeList，然后必须循环通过 el 来执行 getElementsByTagName。有没有办法像 jQuery 一样一次性改变它们？

el = document.querySelectorAll('[id^="mg_row_document"]');
el.getElementsByTagName('td')[2].innerHTML = '';

Answer 1

如果您的 jQuery 选择器以前适合您，则可以通过 querySelectorAll() 重用它，但请记住，它不是一个随时可用的 jQuery 集合。相反，您将拥有一个需要使用循环进行迭代的 NodeList。详细信息在代码片段中评论。

片段

/* target is a NodeList. A NodeList is an
|  array-like object, but not a real array.
|  The first half of this selector is most
|  likely not needed. If given the real HTML 
|  we'd know for sure.
*/
var target = document.querySelectorAll("[id*='mg_row_document'] td:nth-of-type(2)");

// Determine the number of tds in NodeList
var qty = target.length;

/* This for loop is saying:
|  "`i` starts at 0 (i=0)...
|  ...For each iteration (for)...
|  ...while `i` is less than (i < )...
|  ...the total amount of `td`s (qty)...
|  ...`i` will increase by 1 (i++)...
*/
for (let i = 0; i < qty; i++) {

  /* Using bracket notation to specify 
  |  the index position of each `td`.
  |  Each iteration, the `style` property
  |  is used to change each `td` background
  |  color to yellow.
  */
  target[i].style.backgroundColor = 'yellow';
}

table,
td {
  border: 1px solid black;
}

<table id='mg1_documentA'>
  <tr id='mg_row_documentA1'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentA2'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentA3'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentA4'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
</table>

<table id='mg1_documentB'>
  <tr id='mg_row_documentB1'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentB2'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentB3'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentB4'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
</table>

<table id='mg1_documentC'>
  <tr id='mg_row_documentC1'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentC2'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentC3'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
  <tr id='mg_row_documentC4'>
    <td>r1c1</td>
    <td>r1c2</td>
    <td>r1c3</td>
  </tr>
</table>