Descendant selectors
h1 //h1 ?
div p //div//p ?
ul > li //ul/li ?
ul > li > a //ul/li/a
div > * //div/*
:root / ?
:root > body /body
Attribute selectors
#id //[@id="id"] ?
.class //[@class="class"] …kinda
input[type="submit"] //input[@type="submit"]
a#abc[for="xyz"] //a[@id="abc"][@for="xyz"] ?
a[rel] //a[@rel]
a[href^='/'] //a[starts-with(@href, '/')] ?
a[href$='pdf'] //a[ends-with(@href, '.pdf')]
a[href~='://'] //a[contains(@href, '://')] …kinda
Order selectors
ul > li:first-child //ul/li[1] ?
ul > li:nth-child(2) //ul/li[2]
ul > li:last-child //ul/li[last()]
li#id:first-child //li[@id="id"][1]
a:first-child //a[1]
a:last-child //a[last()]
Siblings
h1 ~ ul //h1/following-sibling::ul ?
h1 + ul //h1/following-sibling::ul[1]
h1 ~ #id //h1/following-sibling::[@id="id"]
jQuery
$('ul > li').parent() //ul/li/.. ?
$('li').closest('section') //li/ancestor-or-self::section
$('a').attr('href') //a/@href ?
$('span').text() //span/text()
Other things
h1:not([id]) //h1[not(@id)] ?
Text match //button[text()="Submit"] ?
Text match (substring) //button[contains(text(),"Go")]
Arithmetic //product[@price > 2.50]
Has children //ul[*]
Has children (specific) //ul[li]
Or logic //a[@name or @href] ?
Union (joins results) //a | //div ?
Class check
Xpath doesn’t have the “check if part of space-separated list” operator, so this is the workaround (source):
//div[contains(concat(' ',normalize-space(@class),' '),' foobar ')]
Expressions
Prefixes
Begin your expression with any of these.
// anywhere //hr[@class='edge']
./ relative ./a
/ root /html/body/div
Axes
Separate your steps with /. Use two (//) if you don’t want to select direct children.
/ child //ul/li/a
// descendant //[@id="list"]//a
Steps
A step may have an element name (div) and predicates ([...]). Both are optional.
//div
//div[@name='box']
//[@id='link']
They can also be these other things.
//a/text() #=> "Go home"
//a/@href #=> "index.html"
//a/* #=> All a's child elements
Predicates
Predicates ([...])
Restricts a nodeset only if some condition is true. They can be chained.
//div[true()]
//div[@class="head"]
//div[@class="head"][@id="top"]
Operators
Use comparison and logic operators to make conditionals.
# 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
You can use nodes inside predicates.
# Use them inside functions
//ul[count(li) > 2]
//ul[count(li[@class='hide']) > 0]
# This returns `<ul>` that has a `<li>` child
//ul[li]
Indexing
Use [] with a number, or last() or position().
//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)
Chaining order
Order is significant, these two are different.
a[1][@href='/']
a[@href='/'][1]
Nesting predicates
This returns <section> if it has an <h1> descendant with id='hi'.
//section[//h1[@id='hi']]
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]
Boolean functions
not(expr) # button[not(starts-with(text(),"Submit"))]
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()
Type conversion
string()
number()
boolean()
Axes
Using axes
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 ::.
//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')
Child axis
This is the default axis. This makes //a/b/c work.
# both the same
//ul/li/a
//child::ul/child::li/child::a
# both the same
# this works because `child::li` is truthy, so the predicate succeeds
//ul[li]
//ul[child::li]
# both the same
//ul[count(li) > 2]
//ul[count(child::li) > 2]
Descendant-or-self axis
// is short for the descendant-or-self:: axis.
# both the same
//div//h4
//div/descendant-or-self::h4
# both the same
//ul//[last()]
//ul/descendant-or-self::[last()]
Other axes
There are other axes you can use.
Axis Abbrev Description
ancestor
ancestor-or-self
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
Unions
Use | to join two expressions.
//a | //span
More 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 <section> that directly contains h1#section-name
//section[h1[@id='section-name']]
# Find a <section> that contains h1#section-name
# (Same as above, but use descendant-or-self instead of child)
//section[//*[@id='section-name']]
# like jQuery's $().closest('.box')
./ancestor-or-self::[@class="box"]
# Find <item> and check its attributes
//item[@price > 2*@discount]
转载：http://ricostacruz.com/cheatsheets/xpath.html
转载于:https://www.cnblogs.com/c-x-a/p/6911572.html
