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scalpel

scalpel

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A CSS selector parser.

It parses any valid CSS3 selector into tokens. Try it!

Found a selector that cannot be parsed? Raise an issue.

This parser is implemented using Earley parser algorithm. Read about Writing a CSS selector parser in under 120 LoC.

Note:

This parser could be extended to support the entire CSS grammar. I don't have such a use case. However, should you want to add new grammar, raise an issue.

Usage

import {
  createGenerator,
  createParser
} from 'scalpel';
 
const generator = createGenerator();
const parser = createParser();
 
const tokens: Array<SelectorTokenType | CombinatorTokenType= parser.parse('.foo.bar');
 
// [ 
//   { 
//     type: 'selector', 
//     body: [ 
//       { 
//         type: 'classSelector', 
//         name: 'foo' 
//       }, 
//       { 
//         type: 'classSelector', 
//         name: 'bar' 
//       } 
//     ] 
//   } 
// ] 
 
const selector: string = generator.generate(token);
 
// .foo.bar 
 

Note:

For programmatic type definitions, refer to ./src/types.js.

Token types

Type Description Example
adjacentSiblingCombinator An adjacent sibling combinator. .baz0 + .baz1
attributePresenceSelector An attribute presence selector. [qux]
attributeValueSelector An attribute value selector. [qux=val], [qux~=val]
childCombinator A child combinator. .baz0 > .baz1
classSelector A class selector. .baz
descendantCombinator A descendant combinator. .baz0 .baz1
generalSiblingCombinator A general sibling combinator. .baz0 ~ .baz1
idSelector An ID selector #bar
pseudoClassSelector A pseudo-class selector. :corge, :corge(), :corge(val0, 'val1', "val2")
pseudoElementSelector A pseudo-element selector. ::grault
typeSelector A type selector. foo
universalSelector A universal selector. *

Fields

Tokens have fields that describe additional information about the token. Fields are token type specific.

adjacentSiblingCombinator

Name Description Example
type Name of the token type. "adjacentSiblingCombinator"

attributePresenceSelector

Name Description Example
name Name of the element attribute. "qux" in [qux]
type Name of the token type. "attributePresenceSelector"

attributeValueSelector

Name Description Example
name Name of the element attribute. "qux" in [qux]
operator Operator of the expression. "*=" in [qux*=val]
type Name of the token type. "attributeValueSelector"
value Value of the expression. "val" in [qux=val]

childCombinator

Name Description Example
type Name of the token type. "childCombinator"

classSelector

Name Description Example
name Class name. "baz" in .baz[qux]
type Name of the token type. "classSelector"

descendantCombinator

Name Description Example
type Name of the token type. "descendantCombinator"

generalSiblingCombinator

Name Description Example
type Name of the token type. "generalSiblingCombinator"

idSelector

Name Description Example
name Name of the ID. "bar" in #bar:corge()
type Name of the token type. "idSelector"

pseudoClassSelector

Name Description Example
name Name of the pseudo-class. "corge" in #bar:corge()
parameters Array of parameter values. "var0", "var1" and "var2" in :corge(var0, 'var1', "var2")
type Name of the token type. "pseudoClassSelector"

pseudoElementSelector

Name Description Example
name Name of the pseudo-element. "grault" in #bar::grault
type Name of the token type. "pseudoElementSelector"

typeSelector

Name Description Example
name Name of the node. "foo" in foo#bar.baz
type Name of the token type. "typeSelector"

universalSelector

Name Description Example
type Name of the token type. "universalSelector"

Development

git pull git@github.com:gajus/scalpel.git
cd ./scalpel
npm install
npm run test

The parser grammar is in the ./src/grammar.ne file. After making changes to the parser grammar, you need to compile the parser using npm run compile-grammar command.