javascript - 未捕获的类型错误 : is not a function in Chrome

Question

因此，我正在为网站编写用户脚本，但遇到了此错误 Uncaught TypeError: is not a function 它不会出现在 Firefox 中，但会出现在 Chrome 中。我花了最后一个小时进行调试，但没有成功。

我在下面提供了相关片段来重现 Chrome 中的错误。该脚本应该找到包含文本“下载”的按钮并返回 href。

function getSubmissionSource(){
  var controlBar = document.getElementsByClassName("button submission rounded");
  for (var button of controlBar) { //errors here
    var link = button.getElementsByTagName("a")[0];
    if (link !== undefined && link.textContent == "Download") {
      return link.href;
    }
  }
}
console.log(getSubmissionSource());

<div id="test"">
  <span class="button submission rounded">
    <a href="/view/18251152/" class="prev dotted">Older</a>
  </span>
  <span class="button submission rounded">
    <a href="">-Remove from Favorites</a>
  </span>
  <span class="button submission rounded">
    <a href="">Download</a>
  </span>
  <span class="button submission rounded">
    <a href="">Note user</a></span>
  <span class="button submission rounded">
    <a href="/view/18385008/">Newer</a>
    </span>
</div>

Answer 1

您需要使用for循环来迭代nodelist

function getSubmissionSource(){
  var controlBar = document.getElementsByClassName("button submission rounded");
  for (var i=0,iLen=controlBar.length;i<iLen; i++) { //errors here
    var link = controlBar[i].getElementsByTagName("a")[0];
    if (link !== undefined && link.textContent == "Download") {
      return link.href;
    }
  }
}
console.log(getSubmissionSource());

<div id="test"">
  <span class="button submission rounded">
    <a href="/view/18251152/" class="prev dotted">Older</a>
  </span>
  <span class="button submission rounded">
    <a href="">-Remove from Favorites</a>
  </span>
  <span class="button submission rounded">
    <a href="">Download</a>
  </span>
  <span class="button submission rounded">
    <a href="">Note user</a></span>
  <span class="button submission rounded">
    <a href="/view/18385008/">Newer</a>
    </span>
</div>