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ESQuery is a library for querying the AST output by Esprima for patterns of syntax using a CSS style selector system. Check out the demo:
[demo ](https://estools.github.io/esquery/ )
The following selectors are supported:
* AST node type: `ForStatement`
* [wildcard ](http://dev.w3.org/csswg/selectors4/#universal-selector ): `*`
* [attribute existence ](http://dev.w3.org/csswg/selectors4/#attribute-selectors ): `[attr]`
* [attribute value ](http://dev.w3.org/csswg/selectors4/#attribute-selectors ): `[attr="foo"]` or `[attr=123]`
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* attribute regex: `[attr=/foo.*/]`
* attribute conditions: `[attr!="foo"]` , `[attr>2]` , `[attr<3]` , `[attr>=2]` , or `[attr<=3]`
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* nested attribute: `[attr.level2="foo"]`
* field: `FunctionDeclaration > Identifier.id`
* [First ](http://dev.w3.org/csswg/selectors4/#the-first-child-pseudo ) or [last ](http://dev.w3.org/csswg/selectors4/#the-last-child-pseudo ) child: `:first-child` or `:last-child`
* [nth-child ](http://dev.w3.org/csswg/selectors4/#the-nth-child-pseudo ) (no ax+b support): `:nth-child(2)`
* [nth-last-child ](http://dev.w3.org/csswg/selectors4/#the-nth-last-child-pseudo ) (no ax+b support): `:nth-last-child(1)`
* [descendant ](http://dev.w3.org/csswg/selectors4/#descendant-combinators ): `ancestor descendant`
* [child ](http://dev.w3.org/csswg/selectors4/#child-combinators ): `parent > child`
* [following sibling ](http://dev.w3.org/csswg/selectors4/#general-sibling-combinators ): `node ~ sibling`
* [adjacent sibling ](http://dev.w3.org/csswg/selectors4/#adjacent-sibling-combinators ): `node + adjacent`
* [negation ](http://dev.w3.org/csswg/selectors4/#negation-pseudo ): `:not(ForStatement)`
* [has ](https://drafts.csswg.org/selectors-4/#has-pseudo ): `:has(ForStatement)`
* [matches-any ](http://dev.w3.org/csswg/selectors4/#matches ): `:matches([attr] > :first-child, :last-child)`
* [subject indicator ](http://dev.w3.org/csswg/selectors4/#subject ): `!IfStatement > [name="foo"]`
* class of AST node: `:statement` , `:expression` , `:declaration` , `:function` , or `:pattern`
[![Build Status ](https://travis-ci.org/estools/esquery.png?branch=master )](https://travis-ci.org/estools/esquery)