通过 HTML 标记进行 XPath 搜索答案

【问题标题】：XPath search through HTML tags通过 HTML 标记进行 XPath 搜索
【发布时间】：2011-10-12 08:26:19
【问题描述】：

以下 HTML 显示第 3 次搜索（搜索“Practice Guidelines Professional”）不起作用，因为文本“Practice Guidelines”位于 <strong></strong> 标记之间...是否可以实现 XPath 搜索以绕过 HTML文本之间的标签？

<html>
<head>
<meta http-equiv="X-UA-Compatible" content="chrome=1">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<meta name="apple-mobile-web-app-capable" content="yes">
<meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<title>Xpath Test</title>

<script type="text/javascript">
var search = function (button) {
    var searchTxt = button.value;
    var xpath = '//*[contains(translate(text(),\'ABCDEFGHIJKLMNOPQRSTUVWXYZ\', \'abcdefghijklmnopqrstuvwxyz\'), \'' + searchTxt.toLowerCase() + '\')]';
    var nodes = null;

    if (document.evaluate) { 
        nodes = document.evaluate(
          xpath,
          document,
          null,
          XPathResult.ORDERED_NODE_ITERATOR_TYPE,
          null
        );

        var node = nodes.iterateNext ();
        if (node) {
            while (node) {
                var nodeXpath = createXPathFromElement(node);
                alert("Found!!!\n xpath: " + nodeXpath);
                node = nodes.iterateNext ();
            }
        } else {
            alert("No results found.");
        }
    } else {  
        alert("Your browser does not support the evaluate method!");
    }
  }

  function createXPathFromElement(elm) {
    var allNodes = document.getElementsByTagName('*'); 
    for (segs = []; elm && elm.nodeType == 1; elm = elm.parentNode) 
    {  
        for (i = 1, sib = elm.previousSibling; sib; sib = sib.previousSibling) { 
            if (sib.localName == elm.localName)  i++; 
        };
        segs.unshift(elm.localName.toLowerCase() + '[' + i + ']'); 
    }; 
    return segs.length ? '//' + segs.join('//') : null; 
  }
</script>
</head>

<body>
<table>
    <tr>
        <td>
            <p>&#160;</p><h3><strong><span class="color-1">PRINCIPLES OF PATIENT CARE</span></strong></h3><p class="noindent"><strong><span class="color-1">Evidence-Based Medicine</span></strong> Evidence-based medicine refers to the concept that clinical decisions are formally supported by data, preferably data that are derived from prospectively designed, randomized, controlled clinical trials. This is in sharp contrast to anecdotal experience, which may often be biased. Unless they are attuned to the importance of using larger, more objective studies for making decisions, even the most experienced physicians can be influenced by recent encounters with selected patients. Evidence-based medicine has become an increasingly important part of the routine practice of medicine and has led to the publication of a number of practice guidelines.</p>
            <p>&#160;</p><p class="noindent"><strong><span class="color-1">Practice Guidelines</span></strong> Professional organizations and government agencies are developing formal clinical-practice guidelines to aid physicians and other caregivers in making diagnostic and therapeutic decisions that are evidence-based, cost-effective, and most appropriate to a particular patient and clinical situation. As the evidence base of medicine increases, guidelines can provide a useful framework for managing patients with particular diagnoses or symptoms. They can protect patients—particularly those with inadequate health care benefits—from receiving substandard care. Guidelines can also protect conscientious caregivers from inappropriate charges of malpractice and society from the excessive costs associated with the overuse of medical resources. There are, however, caveats associated with clinical practice guidelines since they tend to oversimplify the complexities of medicine. Furthermore, groups with differing perspectives may develop divergent recommendations regarding issues as basic as the need for periodic sigmoidoscopy in middle-aged persons. Finally, guidelines do not—and cannot be expected to—account for the uniqueness of each individual and his or her illness. The physician’s challenge is to integrate into clinical practice the useful recommendations offered by experts without accepting them blindly or being inappropriately constrained by them.</p>               
        </td>
    </tr>
    <tr>
        <td>
            Search for <input type="button" onclick="search(this)" value="Practice Guidelines" /> Success.
        </td>
    </tr>
    <tr>
        <td>
            Search for <input type="button" onclick="search(this)" value="Professional" /> Success.
        </td>
    </tr>
    <tr>
        <td>
            Search for <input type="button" onclick="search(this)" value="Practice Guidelines Professional" /> No result since text 'Practice Guidelines' is inside &lt;strong&gt;&lt;strong/&gt;, and  'Professional' is out side.     
        </td>
    </tr>
</table>
</body>
</html>

【问题讨论】：

标签： javascript dom xpath html-parsing

【解决方案1】：

是的。您可以为此使用normalize-space()。 （为了便于阅读，换行）

var xpath = "
  //*[
    contains(
      translate(
        normalize-space(.), 
        'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 
        'abcdefghijklmnopqrstuvwxyz'
      ), 
      normalize-space('" + searchTxt.toLowerCase() + "')
    )
  ]
";

请注意，这将找到包含相应文本的节点的整个层次结构，直到并包括<html> 元素。我猜你会对“嵌套最深”的节点感兴趣。

另请注意，您可能希望从 searchTxt 中删除单引号，因为它们会破坏 XPath 表达式。

【讨论】：

【解决方案2】：

可能还有一种递归方法可以查看根元素的 textContent/innerHTML 以查看是否找到匹配项。如果是，则先向下匹配匹配的子节点，以此类推，跟随子节点直到匹配失败，此时已找到包含文本的元素。

也应该适用于文本的多个匹配项。

XPath 可能更快，但可能没有那么广泛的支持（尽管它似乎在所有现代浏览器上）。

【讨论】：