CSS selector specificity calculator
JavaScript
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README.md

specimen

A CSS selector specificity calculator.

usage

npm install specimen
var specimen = require('specimen');

specimen('#home #warning p.message');
//=> [0, 2, 1, 1]
specimen('#home #warning p.message, .footer a[rel=me]:hover');
//=> [ [0,2,1,1], [0,0,3,1] ]

specimen([
  '#home #warning p.message',
  '.footer a[rel=me]:hover'
]);
//=> [ [0,2,1,1], [0,0,3,1] ]

api

specimen(selectors)

Calculates the specificity of one or more CSS selectors. The selectors argument is a string containing one or more selectors, or an array of selector strings.

Returns an array representing the specificity, or undefined if a non-string was given.

For multiple selectors, whether passed as string or array, an array of specificities is returned. Returns undefined if all values in the array would have been undefined.

specimen's specificity

Specificity is represented as a four element array where each element corresponds to a selector category.

The selector categories are, in order of most to least specific:

  • i: inline styles
  • a: IDs
  • b: classes, attributes & psuedo-classes
  • c: elements & pseudo-elements

how it works

A a selector is split up into chunks and sorted into selector categories. The categories are tallied, and the result is specificity: [i, a, b, c].

specimen('#home #warning p.message');
//=> [0, 2, 1, 1]

style="!important"

Specimen calculates selector specificity only; it cannot know the specificity of inline styles. It also cannot account for the use of !important.

gigo

Specimen will attempt to calculate the CSS selector specificty of any string. A result of [0, 0, 0, 0] means the string is probably not a CSS selector, or contains only the universal selector "*" which has no affect on specificity.

credits

Specimen is based heavily on keeganstreet/specificity.

I needed a small specificity module for another project and Keegan Street's specificity fit the bill perfectly. But I also needed a small project to help curb my fear of programming. I decided I didn't need the additional information that specificity provides. I settled on a simpler API and specimen was born.