How Can I Accurately Select CSS Classes Using XPath?

Selecting CSS Classes with XPath: A Comprehensive Guide

The Challenge

Selecting CSS classes with XPath poses a unique challenge as XPath lacks a native equivalent to the CSS class selector. This article explores the intricacies of this issue and provides an efficient solution.

The Wrong Way: Class Equal to

XPath selectors using //*[@class="foo"] fail to select elements with multiple classes or whitespace around the class name.

The Wrong Way: Class Contains

Selectors like //*[contains(@class, "foo")] match elements with classes such as foobar, which is incorrect.

The Right Way: Normalize-Space and Contains

To select elements with specific classes accurately, XPath utilizes the following selector:

//*[contains(concat(" ", normalize-space(@class), " "), " foo ")]

• normalize-space() removes leading and trailing whitespace.
• concat() appends a space before and after the class attribute value.
• contains() checks if the concatenated string includes the target class.

Equivalence and Further Implications

The XPath selector provided is equivalent to the CSS selector *[class~="foo"], which matches elements with classes that contain the target class. Understanding these nuances is crucial for XPath proficiency.

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