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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:


The following selectors are supported:

  • AST node type: ForStatement
  • wildcard: *
  • attribute existence: [attr]
  • attribute value: [attr="foo"] or [attr=123]
  • attribute regex: [attr=/foo.*/] or (with flags) [attr=/foo.*/is]
  • attribute conditions: [attr!="foo"], [attr>2], [attr<3], [attr>=2], or [attr<=3]
  • nested attribute: [attr.level2="foo"]
  • field: FunctionDeclaration >
  • First or last child: :first-child or :last-child
  • nth-child (no ax+b support): :nth-child(2)
  • nth-last-child (no ax+b support): :nth-last-child(1)
  • descendant: ancestor descendant
  • child: parent > child
  • following sibling: node ~ sibling
  • adjacent sibling: node + adjacent
  • negation: :not(ForStatement)
  • has: :has(ForStatement)
  • matches-any: :matches([attr] > :first-child, :last-child)
  • subject indicator: !IfStatement > [name="foo"]
  • class of AST node: :statement, :expression, :declaration, :function, or :pattern

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