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XPath (XML Path Language) is a language for addressing elements in a XML or HTML document. XPath expressions describe paths in a tree represention of the document using various conditions.

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. See the links below for documentation of the XPath language.

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.

Relative paths

Note that relative XPath expressions, 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.

More information