jQuery
New Wave Javascript

One of the selector languages that jQuery supports, as a part of it's expression language is XPath. jQuery supports basic XPath expressions, in addition to CSS 1-3. Here are some samples:

$("/html/body//p")
$("//p")
$("//p/a")
$("//a[@src]")
$("//a[@src='google.com']")

Location Paths

Absolute Paths

$("/html/body//p")
$("/*/body//p")
$("//p/../div")

Relative Paths

$("a",this)
$("p/a",this)

Supported Axes

descendant:: Element has a descendant element

$("//div/descendant::p")
same as: $("//div//p")

child:: Element has a child element

$("//div/child::p")
same as: $("//div/p")

preceding-sibling:: Element has an element before it, on the same axes

$("//div/preceding-sibling::form")

parent:: Selects the parent element of the element

$("//div/parent::div")
same as: $("//div/../div")

self:: Selects the element itself

Supported Predicates

[@*] Has an attribute

$("//div[@*]")

[@foo] Han an attribute of foo

$("//input[@checked]")

[@foo='test'] Attribute foo is equal to test

$("//a[@ref='nofollow']")

[ Nodelist] Element contains a node list, for example:

$("//div[p]")
$("//div[p/a]")

Supported Predicates, but differently

[last()] or [position()=last()] becomes :last

$("p:last")

[ 0] or [position()=0] becomes :eq(0) or :first

$("p:first")
$("p:eq(0)")

[position() < 5] becomes :lt(5)

$("p:lt(5)")

[position() > 2] becomes :gt(2)

$("p:gt(2)")