javascript - 通过索引获取特定元素的文本

Question

我想获取表格倒数第二行的文本，所以我尝试这样做:

var tradeNumEl = $("td.trade-num").length - 2;
console.log($("td.trade-num")[tradeNumEl].text())

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<table>
  <tr>
    <td class="trade-num">100</td>
  </tr>
  <tr>
    <td class="trade-num">101</td>
  </tr>
  <tr>
    <td class="trade-num">102</td>
  </tr>
  <tr>
    <td class="trade-num">103</td>
  </tr>
  <tr>
    <td class="trade-num">104</td>
  </tr>
  <tr>
    <td class="trade-num">105</td>
  </tr>
</table>

然而它给了我:

Uncaught TypeError: $(...)[tradeNumEl].text is not a function

我该如何解决这个问题？这是 fiddle :https://jsfiddle.net/45a9sc6k/4/

Answer 1

按索引访问 jQuery 对象会返回集合中该索引处的 Element 对象。它不返回 jQuery 对象 - 因此你的错误。要解决此问题，请改用 eq():

console.log($("td.trade-num").eq(tradeNumEl).text());

var tradeNumEl = $("td.trade-num").length - 2;
console.log($("td.trade-num").eq(tradeNumEl).text());

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<table>
  <tr>
    <td class="trade-num">100</td>
  </tr>
  <tr>
    <td class="trade-num">101</td>
  </tr>
  <tr>
    <td class="trade-num">102</td>
  </tr>
  <tr>
    <td class="trade-num">103</td>
  </tr>
  <tr>
    <td class="trade-num">104</td>
  </tr>
  <tr>
    <td class="trade-num">105</td>
  </tr>
</table>