Voorbeeld van XPath

In this section, let's learn some basic XPath syntax through examples.

XML example document

We will use this XML document in the following examples:

"books.xml" :

<?xml version="1.0" encoding="ISO-8859-1"?>
<bookstore>
<book category="COOKING">
  <title lang="en">Everyday Italian</title>
  <author>Giada De Laurentiis</author>
  <year>2005</year>
  <price>30.00</price>
</book>
<book category="CHILDREN">
  <title lang="en">Harry Potter</title>
  <author>J K. Rowling</author>
  <year>2005</year>
  <price>29.99</price>
</book>
<book category="WEB">
  <title lang="en">XQuery Kick Start</title>
  <author>James McGovern</author>
  <author>Per Bothner</author>
  <author>Kurt Cagle</author>
  <author>James Linn</author>
  <author>Vaidyanathan Nagarajan</author>
  <year>2003</year>
  <price>49.99</price>
</book>
<book category="WEB">
  <title lang="en">Learning XML</title>
  <author>Erik T. Ray</author>
  <year>2003</year>
  <price>39.95</price>
</book>
</bookstore>

View this "books.xml" file in your browser.

Load XML document

All modern browsers support the method of loading XML documents using XMLHttpRequest.

Code for most modern browsers:

var xmlhttp=new XMLHttpRequest()

Code for old Microsoft browsers (IE 5 and 6):

var xmlhttp=new ActiveXObject("Microsoft.XMLHTTP")

Select nodes

Unfortunately, Internet Explorer and other processors handle XPath differently.

In our example, we include code that is applicable to most mainstream browsers.

Internet Explorer uses the selectNodes() method to select nodes from an XML document:

xmlDoc.selectNodes(xpath);

Firefox, Chrome, Opera, and Safari use the evaluate() method to select nodes from an XML document:

xmlDoc.evaluate(xpath, xmlDoc, null, XPathResult.ANY_TYPE, null);

Select all titles

The following example selects all title nodes:

/bookstore/book/title

Probeer het zelf

Select the title of the first book

The following example selects the title of the first book node under bookstore:

/bookstore/book[1]/title

Probeer het zelf

There is a problem here. The example above produces different results in IE and other browsers.

IE5 and later versions treat [0] as the first node, while according to W3C standards, it should be [1].

To solve the problem of [0] and [1] in IE5+, you can set the language selection (SelectionLanguage) for XPath.

The following example selects the title of the first book node under bookstore:

xml.setProperty("SelectionLanguage","XPath");
xml.selectNodes("/bookstore/book[1]/title");

Probeer het zelf

Select all prices

The following example selects all text within the price nodes:

/bookstore/book/price/text()

Probeer het zelf

Select nodes with a price greater than 35

Het volgende voorbeeld selecteert alle price nodes met een prijs hoger dan 35:

/bookstore/book[price>35]/price

Probeer het zelf

Selecteer title nodes met een prijs hoger dan 35

Het volgende voorbeeld selecteert alle title nodes met een prijs hoger dan 35:

/bookstore/book[price>35]/title

Probeer het zelf