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172 lines
5.1 KiB
Markdown
172 lines
5.1 KiB
Markdown
XPath
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====
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[](https://godoc.org/github.com/antchfx/xpath)
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[](https://coveralls.io/github/antchfx/xpath?branch=master)
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[](https://travis-ci.org/antchfx/xpath)
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[](https://goreportcard.com/report/github.com/antchfx/xpath)
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XPath is Go package provides selecting nodes from XML, HTML or other documents using XPath expression.
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Implementation
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===
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- [htmlquery](https://github.com/antchfx/htmlquery) - an XPath query package for HTML document
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- [xmlquery](https://github.com/antchfx/xmlquery) - an XPath query package for XML document.
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- [jsonquery](https://github.com/antchfx/jsonquery) - an XPath query package for JSON document
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Supported Features
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===
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#### The basic XPath patterns.
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> The basic XPath patterns cover 90% of the cases that most stylesheets will need.
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- `node` : Selects all child elements with nodeName of node.
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- `*` : Selects all child elements.
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- `@attr` : Selects the attribute attr.
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- `@*` : Selects all attributes.
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- `node()` : Matches an org.w3c.dom.Node.
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- `text()` : Matches a org.w3c.dom.Text node.
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- `comment()` : Matches a comment.
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- `.` : Selects the current node.
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- `..` : Selects the parent of current node.
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- `/` : Selects the document node.
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- `a[expr]` : Select only those nodes matching a which also satisfy the expression expr.
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- `a[n]` : Selects the nth matching node matching a When a filter's expression is a number, XPath selects based on position.
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- `a/b` : For each node matching a, add the nodes matching b to the result.
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- `a//b` : For each node matching a, add the descendant nodes matching b to the result.
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- `//b` : Returns elements in the entire document matching b.
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- `a|b` : All nodes matching a or b, union operation(not boolean or).
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- `(a, b, c)` : Evaluates each of its operands and concatenates the resulting sequences, in order, into a single result sequence
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#### Node Axes
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- `child::*` : The child axis selects children of the current node.
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- `descendant::*` : The descendant axis selects descendants of the current node. It is equivalent to '//'.
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- `descendant-or-self::*` : Selects descendants including the current node.
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- `attribute::*` : Selects attributes of the current element. It is equivalent to @*
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- `following-sibling::*` : Selects nodes after the current node.
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- `preceding-sibling::*` : Selects nodes before the current node.
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- `following::*` : Selects the first matching node following in document order, excluding descendants.
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- `preceding::*` : Selects the first matching node preceding in document order, excluding ancestors.
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- `parent::*` : Selects the parent if it matches. The '..' pattern from the core is equivalent to 'parent::node()'.
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- `ancestor::*` : Selects matching ancestors.
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- `ancestor-or-self::*` : Selects ancestors including the current node.
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- `self::*` : Selects the current node. '.' is equivalent to 'self::node()'.
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#### Expressions
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The gxpath supported three types: number, boolean, string.
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- `path` : Selects nodes based on the path.
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- `a = b` : Standard comparisons.
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* a = b True if a equals b.
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* a != b True if a is not equal to b.
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* a < b True if a is less than b.
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* a <= b True if a is less than or equal to b.
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* a > b True if a is greater than b.
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* a >= b True if a is greater than or equal to b.
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- `a + b` : Arithmetic expressions.
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* `- a` Unary minus
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* a + b Add
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* a - b Substract
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* a * b Multiply
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* a div b Divide
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* a mod b Floating point mod, like Java.
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- `a or b` : Boolean `or` operation.
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- `a and b` : Boolean `and` operation.
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- `(expr)` : Parenthesized expressions.
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- `fun(arg1, ..., argn)` : Function calls:
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| Function | Supported |
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| --- | --- |
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`boolean()`| ✓ |
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`ceiling()`| ✓ |
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`choose()`| ✗ |
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`concat()`| ✓ |
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`contains()`| ✓ |
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`count()`| ✓ |
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`current()`| ✗ |
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`document()`| ✗ |
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`element-available()`| ✗ |
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`ends-with()`| ✓ |
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`false()`| ✓ |
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`floor()`| ✓ |
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`format-number()`| ✗ |
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`function-available()`| ✗ |
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`generate-id()`| ✗ |
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`id()`| ✗ |
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`key()`| ✗ |
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`lang()`| ✗ |
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`last()`| ✓ |
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`local-name()`| ✓ |
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`name()`| ✓ |
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`namespace-uri()`| ✓ |
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`normalize-space()`| ✓ |
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`not()`| ✓ |
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`number()`| ✓ |
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`position()`| ✓ |
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`replace()`| ✓ |
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`reverse()`| ✓ |
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`round()`| ✓ |
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`starts-with()`| ✓ |
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`string()`| ✓ |
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`string-length()`| ✓ |
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`substring()`| ✓ |
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`substring-after()`| ✓ |
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`substring-before()`| ✓ |
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`sum()`| ✓ |
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`system-property()`| ✗ |
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`translate()`| ✓ |
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`true()`| ✓ |
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`unparsed-entity-url()` | ✗ |
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Changelogs
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===
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2019-03-19
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- optimize XPath `|` operation performance. [#33](https://github.com/antchfx/xpath/issues/33). Tips: suggest split into multiple subquery if you have a lot of `|` operations.
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2019-01-29
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- improvement `normalize-space` function. [#32](https://github.com/antchfx/xpath/issues/32)
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2018-12-07
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- supports XPath 2.0 Sequence expressions. [#30](https://github.com/antchfx/xpath/pull/30) by [@minherz](https://github.com/minherz). |