XPath

XPath Selectors

Getting started

• Xpath test bed (whitebeam.org)

Test in Firefox or Chrome console:

$x('/html/body')
$x('//h1')
$x('//h1')[0].innerText
$x('//a[text()="XPath"]')[0].click()

Descendant selectors

Order selectors

Attribute selectors

Siblings

jQuery

Misc selectors

XPath Expressions

Steps and axes

Prefixes

Axes

XPath Predicates

Predicates

//div[true()]
//div[@class="head"]
//div[@class="head"][@id="top"]

Restricts a nodeset only if some condition is true. They can be chained.

Operators

# Comparison
//a[@id = "xyz"]
//a[@id != "xyz"]
//a[@price > 25]

# Logic (and/or)
//div[@id="head" and position()=2]
//div[(x and y) or not(z)]

Using nodes

# Use them inside functions
//ul[count(li) > 2]
//ul[count(li[@class='hide']) > 0]

# Returns `<ul>` that has a `<li>` child
//ul[li]

You can use nodes inside predicates.

Indexing

//a[1]                # first <a>
//a[last()]           # last <a>
//ol/li[2]            # second <li>
//ol/li[position()=2] # same as above
//ol/li[position()>1] #:not(:first-child)

Use [] with a number, or last() or position().

Chaining order

a[1][@href='/']
a[@href='/'][1]

Order is significant, these two are different.

Nesting predicates

//section[.//h1[@id='hi']]

This returns <section> if it has an <h1> descendant with id='hi'.

XPath Functions

Node functions

name()            # //[starts-with(name(), 'h')]
text()            # //button[text()="Submit"]
                  # //button/text()
lang(str)
namespace-uri()

count()           # //table[count(tr)=1]
position()        # //ol/li[position()=2]

String functions

contains()        # font[contains(@class,"head")]
starts-with()     # font[starts-with(@class,"head")]
ends-with()       # font[ends-with(@class,"head")]

concat(x,y)
substring(str, start, len)
substring-before("01/02", "/")  #=> 01
substring-after("01/02", "/")   #=> 02
translate()
normalize-space()
string-length()

Boolean functions

not(expr)         # button[not(starts-with(text(),"Submit"))]

Type conversion

string()
number()
boolean()

XPath Axes

Using axes

//ul/li                       # ul > li
//ul/child::li                # ul > li (same)
//ul/following-sibling::li    # ul ~ li
//ul/descendant-or-self::li   # ul li
//ul/ancestor-or-self::li     # $('ul').closest('li')

Steps of an expression are separated by /, usually used to pick child nodes. That’s not always true: you can specify a different “axis” with ::.

Child axis

# both the same
//ul/li/a
//child::ul/child::li/child::a

child:: is the default axis. This makes //a/b/c work.

# both the same
# this works because `child::li` is truthy 
//ul[li]
//ul[child::li]

# both the same
//ul[count(li) > 2]
//ul[count(child::li) > 2]

Descendant-or-self axis

# both the same
//div//h4
//div/descendant-or-self::h4

// is short for the descendant-or-self:: axis.

# both the same
//ul//[last()]
//ul/descendant-or-self::[last()]

Other axes

| attribute | @ | @href is short for attribute::href | | child | | div is short for child::div | | descendant | | | | descendant-or-self | // | // is short for /descendant-or-self::node()/ | | namespace | | |

| self | . | . is short for self::node() | | parent | .. | .. is short for parent::node() |

| following | | | | following-sibling | | | | preceding | | | | preceding-sibling | | | {.headers}

There are other axes you can use.

Unions

//a | //span

Use | to join two expressions.

XPath More examples

Examples

//*                 # all elements
count(//*)          # count all elements
(//h1)[1]/text()    # text of the first h1 heading
//li[span]          # find a <li> with an <span> inside it
                    # ...expands to //li[child::span]
//ul/li/..          # use .. to select a parent

Find a parent

//section[h1[@id='section-name']]

Finds a <section> that directly contains h1#section-name

//section[//h1[@id='section-name']]

Finds a <section> that contains h1#section-name. (Same as above, but uses descendant-or-self instead of child)

Closest

./ancestor-or-self::[@class="box"]

Works like jQuery’s $().closest('.box').

Attributes

//item[@price > 2*@discount]

Finds <item> and check its attributes

Also see

• Devhints (devhints.io)
• Xpath test bed (whitebeam.org)

• Pandoc
• Pandoc
• XPath