XPath: Difference between revisions
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'''XPath''' (XML Path Language) is a language for addressing elements in a XML or HTML document. | '''XPath''' (XML Path Language) is a language for addressing elements in a XML or HTML document. [[XPathExpression|XPathExpressions]] describe paths in a tree represention of the document. | ||
XPath is very fast compared to manual DOM traversal (see e.g. [http://ejohn.org/blog/getelementsbyclassname-speed-comparison/ getElementsByClassName Speed Comparison]). | XPath is very fast compared to manual DOM traversal (see e.g. [http://ejohn.org/blog/getelementsbyclassname-speed-comparison/ getElementsByClassName Speed Comparison]). | ||
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== Using XPath in Greasemonkey == | == Using XPath in Greasemonkey == | ||
The most convenient way to use XPath in Greasemonkey scripts is with a [[ | The most convenient way to use XPath in Greasemonkey scripts is with a [[XPath_Helper|helper function]]. | ||
The insides of that function illustrate the less convenient way. | |||
The native method is through the <code>document.evaluate</code> function. | |||
== | == XPathResult resultTypes == | ||
* [[XPathResult#resultType_Constants|resultType Constants]] | |||
* [http://developer.mozilla.org/en/Introduction_to_using_XPath_in_JavaScript#XPathResult_Defined_Constants Further reading at Mozilla Developer Center] | |||
== | == Relative paths == | ||
Note that relative [[XPathExpression|XPathExpressions]], that start from some specific node, do not begin with a <code>/</code>. Start them with a period, e.g. <code>.//a</code>, or an axis, e.g. <code>descendant::a</code>. The default axis is <code>child</code>, so just <code>a</code> works to find an immediate descendant. | |||
== Links == | == Links == | ||
Latest revision as of 19:48, 3 November 2017
XPath (XML Path Language) is a language for addressing elements in a XML or HTML document. XPathExpressions describe paths in a tree represention of the document.
XPath is very fast compared to manual DOM traversal (see e.g. getElementsByClassName Speed Comparison).
This page is intended for tips and gotchas related to using XPath in Greasemonkey scripts, not complete documentation. See the links below for that.
Using XPath in Greasemonkey
The most convenient way to use XPath in Greasemonkey scripts is with a helper function.
The insides of that function illustrate the less convenient way.
The native method is through the document.evaluate function.
XPathResult resultTypes
Relative paths
Note that relative XPathExpressions, that start from some specific node, do not begin with a /. Start them with a period, e.g. .//a, or an axis, e.g. descendant::a. The default axis is child, so just a works to find an immediate descendant.
