Why Doesn\'t `h3:nth-child(1):contains(\'a\')` Work as Expected?

Selector h3:nth-child(1):contains('a') Ineffectiveness

Despite its apparent syntax, the selector h3:nth-child(1):contains('a') fails to perform its intended function.

Under the Hood

Upon further investigation, it is revealed that h3:nth-child(1) correctly targets the first h3 element within its parent container. However, h3:nth-child(1):contains('a') produces no results because the :contains() selector, originally intended as a CSS3 feature, has been omitted from the CSS specification.

:contains() was designed to match elements containing a specific text pattern. Unfortunately, the way it functioned posed challenges to browser performance and led to over-selection issues. For instance, matching an element using :contains() would also match all its ancestors, potentially resulting in unexpected behavior when combined with universal selectors or certain style properties.

Alternative Approaches

Due to the absence of a suitable CSS selector alternative, achieving the desired result requires alternative methods. Modifying the HTML structure or utilizing jQuery's implementation of :contains() can be explored:

• Select an h3 element as the first child within its parent and with text containing 'a'.

jQuery or Selenium RC Considerations

For jQuery and Selenium RC users, :contains() is implemented in the Sizzle selector engine, providing similar functionality to the CSS3 specification. However, it is recommended to use this selector judiciously to avoid unexpected selections.

A Refinement

Lastly, h3:nth-child(1) can be substituted with h3:first-child for enhanced browser compatibility as a CSS2 selector.

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