Improve xpath
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Rico Sta. Cruz
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xpath.md
139
xpath.md
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@ -6,33 +6,35 @@ layout: default
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CSS equivalents
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---------------
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| CSS | Xpath |
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| --- | --- |
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| `div p` | `//div//p` |
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| `ul > li` | `//ul/li` |
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| `div > *` | `//div/*` |
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| `h1 ~ ul` | `//h1/following-sibling::ul` |
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| `h1 ~ #id` | `//h1/following-sibling::[@id="id"]` |
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| --- | --- |
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| `:root` | `/` |
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| `:root > body` | `/body` |
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| --- | --- |
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| `input[type="submit"]` | `//input[@type="submit"]` |
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| `a[href^='/']` | `//a[starts-with(@href, '/')]` |
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| `a[href$='pdf']` | `//a[ends-with(@href, '.pdf')]` |
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| --- | --- |
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| `#id` | `//[@id="id"]` |
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| `.class` | `//[@class="class"]` *...see below* |
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| --- | --- |
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| `ul > li:first-child` | `//ul/li[1]` |
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| `ul > li:nth-child(2)` | `//ul/li[2]` |
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| `ul > li:last-child` | `//ul/li[last()]` |
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| --- | --- |
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| `li#id:first-child` | `//li[@id="id"][1]` |
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| --- | --- |
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| `a:first-child` | `//a[1]` |
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| `a:last-child` | `//a[last()]` |
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| `li:first-of-type` | `//li[not(preceding-sibling::li)]` |
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| CSS | Xpath | ? |
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| --- | --- | ---: |
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| `ul > li` | `//ul/li` | [?](#axes) |
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| `div > *` | `//div/*` | |
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| --- | --- | |
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| `div p` | `//div//p` | [?](#axes) |
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| --- | --- | |
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| `h1 ~ ul` | `//h1/following-sibling::ul` | [?](#other-axes) |
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| `h1 ~ #id` | `//h1/following-sibling::[@id="id"]` | |
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| --- | --- | |
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| `:root` | `/` | [?](#prefixes) |
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| `:root > body` | `/body` | |
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| --- | --- | |
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| `input[type="submit"]` | `//input[@type="submit"]` | [?](#predicates) |
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| `a[href^='/']` | `//a[starts-with(@href, '/')]` | [?](#string-functions) |
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| `a[href$='pdf']` | `//a[ends-with(@href, '.pdf')]` | |
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| --- | --- | |
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| `#id` | `//[@id="id"]` | |
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| `.class` | `//[@class="class"]` *...see below* | |
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| --- | --- | |
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| `ul > li:first-child` | `//ul/li[1]` | [?](#indexing) |
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| `ul > li:nth-child(2)` | `//ul/li[2]` | |
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| `ul > li:last-child` | `//ul/li[last()]` | |
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| --- | --- | |
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| `li#id:first-child` | `//li[@id="id"][1]` | [?](#chaining-order) |
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| --- | --- | |
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| `a:first-child` | `//a[1]` | |
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| `a:last-child` | `//a[last()]` | |
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| `li:first-of-type` | `//li[not(preceding-sibling::li)]` | |
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{:.greycode.no-head}
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### Class check
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@ -42,15 +44,22 @@ Xpath doesn't have the "check if part of space-separated list" operator, so this
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//div[contains(concat(' ',normalize-space(@class),' '),' foobar ')]
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```
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### jQuery equivalents
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### Other stuff
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For things that CSS alone can't do.
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| jQuery | Xpath |
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| ------ | --- |
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| `$('ul > li').parent()` | `//ul/li/..` |
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| `$('li').closest('section')` | `//li/ancestor-or-self::section` |
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| ---- | ---- |
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| `$('a').attr('href')` | `//a/@href` |
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| `$('span').text()` | `//span/text()` |
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| ---- | ---- |
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| Text match | `//button[text()="Submit"]` |
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| Text match (substring) | `//button[contains(text(),"Go")]` |
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| Arithmetic | `//product[@price > 2.50]` |
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| Has children | `//ul[*]` |
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| Has children (specific) | `//ul[li]` |
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{:.greycode.no-head}
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@ -68,7 +77,7 @@ Begin your expression with any of these.
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{:.greycode.no-head}
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### Axes
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Separate your steps with `/`. Use two (`//`) if you don't want direct descendants.
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Separate your steps with `/`. Use two (`//`) if you don't want to select direct children.
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| Axis | Example |
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| --- | --- |
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@ -76,10 +85,18 @@ Separate your steps with `/`. Use two (`//`) if you don't want direct descendant
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| `//` *descendant* | `//[@id="list"]//a` |
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{:.greycode.no-head}
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### Selecting node data
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### Steps
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A step may have an element name (`div`) and [predicates](#predicate) (`[...]`). Both are optional.
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```sh
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//div
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//div[@name='box']
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//[@id='link']
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```
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They can also be these other things.
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```sh
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//a #=> <a>
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//a/text() #=> "Go home"
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//a/@href #=> "index.html"
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//a/* #=> All a's child elements
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@ -88,7 +105,7 @@ Separate your steps with `/`. Use two (`//`) if you don't want direct descendant
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Predicates
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----------
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### Predicates (`[]`)
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### Predicates (`[...]`)
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Restricts a nodeset only if some condition is true. They can be chained.
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```sh
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@ -98,7 +115,7 @@ Restricts a nodeset only if some condition is true. They can be chained.
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```
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### Operators
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Use operators to make conditionals.
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Use comparison and logic operators to make conditionals.
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```sh
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# Comparison
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@ -134,10 +151,11 @@ Use `[]` with a number, or `last()` or `position()`.
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//a[1] # first <a>
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//a[last()] # last <a>
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//ol/li[2] # second <li>
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//ol/li[position()=2] # ...same as above
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//ol/li[position()=2] # same as above
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//ol/li[position()>1] # :not(:first-child)
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```
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### Predicate order
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### Chaining order
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Order is significant, these two are different.
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```sh
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@ -172,7 +190,7 @@ position() # //ol/li[position()=2]
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### Boolean functions
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```sh
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not(expr) # button[not(text()="Submit")]
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not(expr) # button[not(starts-with(text(),"Submit"))]
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```
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### String functions
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@ -202,38 +220,61 @@ boolean()
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Axes
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----
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### The / separator
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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 `::`.
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```sh
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//ul/li
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//div/h1/span
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//ul/li # $('ul > li')
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//ul/ancestor-or-self::li # $('ul').closest('li')
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```
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{:.light}
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### Descendant-or-self axis
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When you use `//` for descendants, this is short or `/descendant-or-self::`.
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When you use `//` for descendants, this is short for the `descendant-or-self::` axis.
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```sh
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# both the same
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//div//h4
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//div/descendant-or-self::h4
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```
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```sh
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# both the same
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//ul//[last()]
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//ul/descendant-or-self::[last()]
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```
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### Child axis
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When no axis is specifid, a step with a `name` is short for `child::name`. This is what makes `//a/b/c` work.
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When axis is not specified, a `name` is short for `child::name`. This is what makes `//a/b/c` work.
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```sh
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# both the same
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//ul/li/a
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//ul/child::li/child::a
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//child::ul/child::li/child::a
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```
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```sh
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# both the same
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# this works because `child::li` is truthy, so the predicate succeeds
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//ul[li]
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//ul[child::li]
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```
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```sh
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# both the same
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//ul[count(li) > 2]
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//ul[count(child::li) > 2]
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```
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### Attribute axis
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When you use `@` for attributes, that's short for the `attribute::` axis.
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```sh
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# both the same
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//a/@href
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//a/attribute::href
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# both the same
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//div[@id="box"]
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//div[attribute::id="box"]
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```
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@ -267,20 +308,15 @@ More examples
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```sh
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//* # all elements
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count(//*) # count all elements
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//h1[1]/text() # hext of the first h1 heading
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//li[span] # Find a <li> with an <span> inside it
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//h1[1]/text() # text of the first h1 heading
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//li[span] # find a <li> with an <span> inside it
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# ...expands to //li[child::span]
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//ul/li/.. # use .. to select a parent
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```
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```sh
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# Find a <section> that directly contains h1#section-name
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//section[child::h1[@id='section-name']]
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```
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```sh
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# like jQuery's $().closest('.box')
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./ancestor-or-self::[@class="box"]
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//section[h1[@id='section-name']]
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```
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```sh
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@ -289,6 +325,11 @@ count(//*) # count all elements
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//section[//*[@id='section-name']]
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```
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```sh
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# like jQuery's $().closest('.box')
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./ancestor-or-self::[@class="box"]
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```
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```sh
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# Find <item> and check its attributes
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//item[@price > 2*@discount]
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