最近在搞puppeteer的自动化，有很多地方需要用到CSS Selector，但是某些地方又是用Xpath方便，金手指放一下，备查：
Test queries in the Xpath test bed:
- Xpath test bed (whitebeam.org)
Browser console
$x("//div")
Works in Firefox and Chrome.
#Selectors
Descendant selectors
h1 | //h1 | |
|---|---|---|
div p | `//div//p | |
ul > li | `//ul/li | |
ul > li > a | //ul/li/a | |
div > * | //div/* | |
:root | `/ | |
:root > body | /body |
Attribute selectors
#id | //*[@id="id"] | |
|---|---|---|
.class | //*[@class="class"] …kinda | |
input[type="submit"] | //input[@type="submit"] | |
a#abc[for="xyz"] | `//a[@id=“abc”][@for=“xyz”] | |
a[rel] | //a[@rel] | |
a[href^='/'] | `//a[starts-with(@href, ‘/’)] | |
a[href$='pdf'] | //a[ends-with(@href, '.pdf')] | |
a[href*='://'] | //a[contains(@href, '://')] | |
a[rel~='help'] | //a[contains(@rel, 'help')] …kinda |
Order selectors
ul > li:first-of-type | `//ul/li[1] | |
|---|---|---|
ul > li:nth-of-type(2) | //ul/li[2] | |
ul > li:last-of-type | //ul/li[last()] | |
li#id:first-of-type | `//li[1][@id=“id”] | |
a:first-child | //*[1][name()="a"] | |
a:last-child | //*[last()][name()="a"] |
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
//div[contains(concat(' ',normalize-space(@class),' '),' foobar ')]
Xpath doesn’t have the “check if part of space-separated list” operator, so this is the workaround (source).
#Expressions
Steps and axes
// | ul | / | a[@id='link'] |
|---|---|---|---|
| Axis | Step | Axis | Step |
Prefixes
| Prefix | Example | What |
|---|---|---|
// | //hr[@class='edge'] | Anywhere |
./ | ./a | Relative |
/ | /html/body/div | Root |
Begin your expression with any of these.
Axes
| Axis | Example | What |
|---|---|---|
/ | //ul/li/a | Child |
// | //[@id="list"]//a | Descendant |
Separate your steps with /. Use two (//) if you don’t want to select direct children.
Steps
//div
//div[@name='box']
//[@id='link']
A step may have an element name (div) and predicates ([...]). Both are optional. They can also be these other things:
//a/text() #=> "Go home"
//a/@href #=> "index.html"
//a/* #=> All a's child elements
#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)]
Use comparison and logic operators to make conditionals.
Using nodes
# Use them inside functions
//ul[count(li) > 2]
//ul[count(li[@class='hide']) > 0]
# This 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-of-type)
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'.
#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
//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 ::.
// | ul | /child:: | li |
|---|---|---|---|
| Axis | Step | Axis | Step |
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, 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
# 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
| Axis | Abbrev | Notes |
|---|---|---|
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 |
There are other axes you can use.
Unions
//a | //span
Use | to join two expressions.
#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
#References
- Xpath test bed (whitebeam.org)