Calculate the CSS specificity (a, b, c) of a selector — a for ID selectors,
b for classes/attributes/pseudo-classes, c for type selectors/pseudo-elements.
Modern selectors are handled per the
spec. The Rust counterpart of
the specificity npm package. Zero
dependencies and #![no_std].
use specificity::{specificity, Specificity};
assert_eq!(specificity("#id .cls a"), Specificity::new(1, 1, 1));
assert_eq!(specificity(":is(.a, #b)"), Specificity::new(1, 0, 0)); // max of the args
assert_eq!(specificity(":where(.a)"), Specificity::new(0, 0, 0)); // contributes nothing
// Specificity is `Ord`, so selectors compare directly.
assert!(specificity("#id") > specificity(".a.b.c"));CSS linters, cascade-analysis tools, devtools, and CSS-in-JS engines all need to
know how strongly a selector matches. The rules are small but full of corners
(:is/:not/:has take the most specific argument, :where is free, ::part
ignores its argument, namespaces and escapes don't fool the counter). Rust had this
only buried inside full CSS engines; this is the focused, dependency-free piece.
[dependencies]
specificity = "0.1"| Item | Purpose |
|---|---|
specificity(selector) |
The Specificity of a single complex selector (max of a list) |
specificity_list(list) |
One Specificity per comma-separated selector |
Specificity { a, b, c } |
The components; implements Ord (a, then b, then c) and Display ("a,b,c") |
a= ID selectors;b= classes, attribute selectors, pseudo-classes;c= type selectors and pseudo-elements. The universal*and combinators add nothing.:is(),:not(),:has()(and:matches()/:-*-any()) contribute the specificity of their most specific argument;:where()contributes nothing.:nth-child()/:nth-last-child()are pseudo-classes; an… of Sargument adds the most specific selector inS.- Pseudo-elements (
::before,::part(x), the legacy single-colon:before, …) count asc, and their functional arguments are ignored. - Namespace prefixes (
svg|a,*|div) and CSS escapes (.foo\.bar) are parsed correctly, and CSS/* … */comments are ignored.
Where keeganstreet specificity diverges from the CSS spec, this crate follows the
spec: :matches() / :-*-any() are treated as aliases of :is() (most specific
argument, not a plain pseudo-class), and a namespaced universal such as *|*
contributes nothing. CSS Modules' :global() / :local() are supported, taking
their argument's specificity.
This project follows the all-contributors specification. Contributions of any kind are welcome — code, docs, bug reports, ideas, reviews! See the emoji key for how each contribution is recognized, and open a PR or issue to get involved.
Thanks goes to these wonderful people:
 Tung Tran 💻 🚧 |
Licensed under either of Apache-2.0 or MIT at your option.