将document.evaluate()的document.evaluate()作为contextNode使用不起作用

Question

在使用document.evaluate时，我试图再次使用xpathResult作为类似于所附示例的contextNode，但没有成功，我错在哪里？

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const getAllLiButton = document.querySelector("#get-all-li");
const getTitleAndTextButton = document.querySelector("#get-title-text");

getAllLiButton.addEventListener("click", getAllLi);
getTitleAndTextButton.addEventListener("click", getTitleAndText);

function getAllLi() {
  var records = [];

  let topLevelResults = document.evaluate("/html/body/ul/li", document, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);

  var levelResult = topLevelResults.iterateNext();
  while (levelResult) {
    records.push(levelResult);
    
    levelResult = topLevelResults.iterateNext();
  }

  console.log(records);
}

function getTitleAndText() {
  let topLevelResults = document.evaluate("/html/body/ul/li", document, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);

  var levelResult = topLevelResults.iterateNext();

  let titleText = document.evaluate("/h3", levelResult, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
  console.log(titleText);

  let textBox = document.evaluate("/span", levelResult, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
  console.log(textBox);
}

<button id="get-all-li">Get all li (works)</button>
<button id="get-title-text">Get single Title & Text (not works)</button>

<ul>
  <li><h3>Title #1</h3><span>some text</span></li>
  <li><h3>Title #2</h3><span>some text</span></li>
  <li><h3>Title #3</h3><span>some text</span></li>
  <li><h3>Title #4</h3><span>some text</span></li>
  <li><h3>Title #5</h3><span>some text</span></li>
</ul>

​

提前感谢您的帮助！

Answer 1

正如文档中所报道的

document.evaluate(".//h3", levelResult, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null)

.//h3 xpathExpression对于指示查询应该从上下文节点(levelResult)开始非常重要。

​

const getAllLiButton = document.querySelector("#get-all-li");
const getTitleAndTextButton = document.querySelector("#get-title-text");

getAllLiButton.addEventListener("click", getAllLi);
getTitleAndTextButton.addEventListener("click", getTitleAndText);

function getAllLi() {
    var records = [];

    let topLevelResults = document.evaluate("/html/body/ul/li", document, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);

    var levelResult = topLevelResults.iterateNext();
    while (levelResult) {
        records.push(levelResult);

        levelResult = topLevelResults.iterateNext();
    }

    console.log(records);
}

function getTitleAndText() {
    let topLevelResults = document.evaluate("/html/body/ul/li", document, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);

    var levelResult = topLevelResults.iterateNext();

    let titleText = document.evaluate(".//h3", levelResult, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
    titleText = titleText.iterateNext();
    console.log(titleText.textContent);

    let textBox = document.evaluate(".//span", levelResult, null, XPathResult.ORDERED_NODE_ITERATOR_TYPE, null);
    textBox = textBox.iterateNext();
    console.log(textBox.textContent);
}

<button id="get-all-li">Get all li (works)</button>
<button id="get-title-text">Get single Title & Text (not works)</button>

<ul>
    <li><h3>Title #1</h3><span>some text</span></li>
    <li><h3>Title #2</h3><span>some text</span></li>
    <li><h3>Title #3</h3><span>some text</span></li>
    <li><h3>Title #4</h3><span>some text</span></li>
    <li><h3>Title #5</h3><span>some text</span></li>
</ul>

​