XML — XPath

Basic XPath

/bookstore/book           # All books
/bookstore/book[1]        # First book
/bookstore/book[last()]   # Last book

XPath Syntax

Expression	Description
nodename	All nodes
/	Root node
//	Any node
.	Current node
..	Parent node
@	Attribute

Predicates

/bookstore/book[1]                    # First book
/bookstore/book[last()]               # Last book
/bookstore/book[position()<3]         # First 2 books
/bookstore/book[@genre='fiction']     # Fiction books
/bookstore/book[price>30]             # Books over 30

Axes

Axis	Description
ancestor	All ancestors
ancestor-or-self	Ancestors + current
child	Direct children
descendant	All descendants
following	All following nodes
preceding	All preceding nodes
self	Current node

Functions

Function	Description
count()	Count nodes
sum()	Sum values
text()	Text content
contains()	String contains
starts-with()	String starts with

Using XPath in JavaScript

var result = xmlDoc.evaluate(
    "/bookstore/book/title",
    xmlDoc,
    null,
    XPathResult.ANY_TYPE,
    null
);

Mini Practice

1. Write basic XPath expressions
2. Use predicates to filter
3. Use axes to navigate
4. Combine functions with XPath

Up Next

Continue with XQuery — querying XML data with XQuery.