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<table width="100%" summary="page for querySelectorAll {selectr}"><tr><td>querySelectorAll {selectr}</td><td style="text-align: right;">R Documentation</td></tr></table>

<h2>
Find nodes that match a group of CSS selectors in an XML tree.
</h2>

<h3>Description</h3>

<p>The purpose of these functions is to mimic the functionality of the
<code>querySelector</code> and <code>querySelectorAll</code> functions present in
Internet browsers. This is so we can succinctly query an XML tree for
nodes matching a CSS selector.
</p>
<p>Namespaced functions <code>querySelectorNS</code> and
<code>querySelectorAllNS</code> are also provided to search relative to a
given namespace.
</p>

<h3>Usage</h3>

<pre>
querySelector(doc, selector, ns = NULL, ...)
querySelectorAll(doc, selector, ns = NULL, ...)
querySelectorNS(doc, selector, ns,
                prefix = "descendant-or-self::", ...)
querySelectorAllNS(doc, selector, ns,
                   prefix = "descendant-or-self::", ...)
</pre>

<h3>Arguments</h3>

<p>The XML document or node to be evaluated against.
</p>
</td></tr>
<tr valign="top"><td><code>selector</code></td>
<td>

<p>A selector used to query <code>doc</code>. This must be a single character
string.
</p>
</td></tr>
<tr valign="top"><td><code>ns</code></td>
<td>

<p>The namespace that the query will be filtered to. This is a named
list or vector which has as its name a namespace, and its value is
the namespace URI. This can be ignored for the un-namespaced
functions.
</p>
</td></tr>
<tr valign="top"><td><code>prefix</code></td>
<td>

<p>The prefix to apply to the resulting XPath expression. The default
or <code>""</code> are most commonly used.
</p>
</td></tr>
<tr valign="top"><td><code>...</code></td>
<td>

<p>Parameters to be passed onto <code>css_to_xpath</code>.
</p>
</td></tr>
</table>

<h3>Details</h3>

<p>The <code>querySelectorNS</code> and <code>querySelectorAllNS</code> functions are
convenience functions for working with namespaced documents. They
filter out all content that does not belong within the given
namespaces. Note that when searching for particular elements in a
selector, they must have a namespace prefix, e.g. <code>"svg|g"</code>.
</p>
<p>The namespace argument, <code>ns</code>, is simply passed on to
<code><a href="../../XML/html/getNodeSet.html">getNodeSet</a></code> or <code><a href="../../xml2/html/xml_find_all.html">xml_find_all</a></code> if
it is necessary to use a namespace present within the document. This
can be ignored for content lacking a namespace, which is usually the
case when using <code>querySelector</code> or <code>querySelectorAll</code>.
</p>

<h3>Value</h3>

<p>For <code>querySelector</code>, the result is a single node that represents
the first matched node from a selector. If no matching nodes are
found, <code>NULL</code> is returned.
</p>
<p>For <code>querySelectorAll</code>, the result is a list of XML nodes. This
list may be empty in the case that no match is found.
</p>
<p>The <code>querySelectorNS</code> and <code>querySelectorAllNS</code> functions
return the same type of content as their un-namespaced counterparts.
</p>

<h3>Author(s)</h3>

<p>Simon Potter
</p>

<h3>References</h3>

<p>CSS3 Selectors <a href="https://www.w3.org/TR/css3-selectors/">https://www.w3.org/TR/css3-selectors/</a>, XPath
<a href="https://www.w3.org/TR/xpath/">https://www.w3.org/TR/xpath/</a>, querySelectorAll
<a href="https://developer.mozilla.org/en-US/docs/DOM/Document.querySelectorAll">https://developer.mozilla.org/en-US/docs/DOM/Document.querySelectorAll</a>
and <a href="http://www.w3.org/TR/selectors-api/#interface-definitions">http://www.w3.org/TR/selectors-api/#interface-definitions</a>.
</p>

<h3>Examples</h3>

<pre>
  hasXML &lt;- require(XML)
  hasxml2 &lt;- require(xml2)

if (!hasXML &amp;&amp; !hasxml2)
    return() # can't demo without XML or xml2 packages present

parseFn &lt;- if (hasXML) xmlParse else read_xml
  # Demo for working with the XML package (if present, otherwise xml2)
  exdoc &lt;- parseFn('&lt;a&gt;&lt;b class="aclass"/&gt;&lt;c id="anid"/&gt;&lt;/a&gt;')
  querySelector(exdoc, "#anid")   # Returns the matching node
  querySelector(exdoc, ".aclass") # Returns the matching node
  querySelector(exdoc, "b, c")    # First match from grouped selection
  querySelectorAll(exdoc, "b, c") # Grouped selection
  querySelectorAll(exdoc, "b")    # A list of length one
  querySelector(exdoc, "d")       # No match
  querySelectorAll(exdoc, "d")    # No match

# Read in a document where two namespaces are being set:
  # SVG and MathML
  svgdoc &lt;- parseFn(system.file("demos/svg-mathml.svg",
                                package = "selectr"))
  # Search for &lt;script/&gt; elements in the SVG namespace
  querySelectorNS(svgdoc, "svg|script",
                  c(svg = "http://www.w3.org/2000/svg"))
  querySelectorAllNS(svgdoc, "svg|script",
                     c(svg = "http://www.w3.org/2000/svg"))
  # MathML content is *within* SVG content,
  # search for &lt;mtext&gt; elements within the MathML namespace
  querySelectorNS(svgdoc, "math|mtext",
                  c(math = "http://www.w3.org/1998/Math/MathML"))
  querySelectorAllNS(svgdoc, "math|mtext",
                     c(math = "http://www.w3.org/1998/Math/MathML"))
  # Search for *both* SVG and MathML content
  querySelectorAllNS(svgdoc, "svg|script, math|mo",
                     c(svg = "http://www.w3.org/2000/svg",
                       math = "http://www.w3.org/1998/Math/MathML"))

if (!hasXML)
    return() # already demo'd xml2

# Demo for working with the xml2 package
  exdoc &lt;- read_xml('&lt;a&gt;&lt;b class="aclass"/&gt;&lt;c id="anid"/&gt;&lt;/a&gt;')
  querySelector(exdoc, "#anid")   # Returns the matching node
  querySelector(exdoc, ".aclass") # Returns the matching node
  querySelector(exdoc, "b, c")    # First match from grouped selection
  querySelectorAll(exdoc, "b, c") # Grouped selection
  querySelectorAll(exdoc, "b")    # A list of length one
  querySelector(exdoc, "d")       # No match
  querySelectorAll(exdoc, "d")    # No match

# Read in a document where two namespaces are being set:
  # SVG and MathML
  svgdoc &lt;- read_xml(system.file("demos/svg-mathml.svg",
                                 package = "selectr"))
  # Search for &lt;script/&gt; elements in the SVG namespace
  querySelectorNS(svgdoc, "svg|script",
                  c(svg = "http://www.w3.org/2000/svg"))
  querySelectorAllNS(svgdoc, "svg|script",
                     c(svg = "http://www.w3.org/2000/svg"))
  # MathML content is *within* SVG content,
  # search for &lt;mtext&gt; elements within the MathML namespace
  querySelectorNS(svgdoc, "math|mtext",
                  c(math = "http://www.w3.org/1998/Math/MathML"))
  querySelectorAllNS(svgdoc, "math|mtext",
                     c(math = "http://www.w3.org/1998/Math/MathML"))
  # Search for *both* SVG and MathML content
  querySelectorAllNS(svgdoc, "svg|script, math|mo",
                     c(svg = "http://www.w3.org/2000/svg",
                       math = "http://www.w3.org/1998/Math/MathML"))
</pre>

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