Skip to content


Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?

Latest commit


Git stats


Failed to load latest commit information.

About CLSS

CLSS is a DOM traversal engine based on CSS selectors. It makes use of the Plump-DOM and is used by lQuery.

How To

Load CLSS through Quicklisp or ASDF:

(ql:quickload :clss)

Using a standard CSS selector you can retrieve a vector of nodes from the DOM:

(clss:select "img" (plump:parse "<div><p>A beautiful image: <img src="//" alt="image" /></p></div>"))

CLSS implements Level 3 selectors and offers most of the features from the spec. Some things were left out as they make no sense outside a CSS context. As Plump supports XML as well as HTML, it also includes special handling for a few nodes that are not elements and are thus not reachable by standard CSS selectors. In order to solve this problem, CLSS adds an extra operator, the ^ caret. The caret is followed by a Plump-DOM class-name and will then match any elements that conform to a typep test against it.

(clss:select "^CDATA" (plump:parse "<foo><![CDATA[bar]]></foo>"))

CSS selectors in themselves also don't support XML namespaces due to the ambiguity arising with pseudo-selectors. CLSS solves this by interpreting a double colon as a name. Thus, a tag with the name of foo:bar is selected by foo::bar.

CLSS attempts to be a fast engine and various parts of it have been tuned for this purpose, which limits the extensibility of CLSS a bit. However, it is still possible to f.e. programmatically construct a selector.

Extending CLSS

Using define-pseudo-selector you can add your own extensions to CLSS:

(clss:define-pseudo-selector outside-link (node)
  (let ((href (plump:attribute node "href")))
    (and href (cl-ppcre:scan "^(http|https)://" href))))

(clss:select "a:outside-link" (plump:parse "<foo><a href=\"/baloney\"/><a href=\"\"/></foo>"))


CSS Like Simple Selectors. A Common Lisp DOM tree search engine based on CSS selectors.







No releases published


No packages published

Contributors 4