regexp-to-ast

Parses a Regular Expression and outputs an AST

Usage no npm install needed!

<script type="module">
  import regexpToAst from 'https://cdn.skypack.dev/regexp-to-ast';
</script>

README

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regexp-to-ast

Reads a JavaScript Regular Expression literal(text) and outputs an Abstract Syntax Tree.

Installation

  • npm
      npm install regexp-to-ast
  • Browser
      <script src="https://unpkg.com/regexp-to-ast/lib/parser.js"></script>

API

The API is defined as a TypeScript definition file.

Usage

  • Parsing to an AST:

    const RegExpParser = require("regexp-to-ast").RegExpParser
const regexpParser = new RegExpParser.parser()

// from a regexp text
const astOutput = regexpParser.pattern("/a|b|c/g")

// text from regexp instance.
const input2 = /a|b/.toString()
// The same parser instance can be reused
const anotherAstOutput = regexpParser.pattern(input2)

  • Visiting the AST:

    // parse to an AST as before.
const { RegExpParser, BaseRegExpVisitor } = require("regexp-to-ast")
const regexpParser = new RegExpParser.parser()
const regExpAst = regexpParser.pattern("/a|b|c/g")

// Override the visitor methods to add your logic.
class MyRegExpVisitor extends BaseRegExpVisitor {
    visitPattern(node) {}

    visitFlags(node) {}

    visitDisjunction(node) {}

    visitAlternative(node) {}

    // Assertion
    visitStartAnchor(node) {}

    visitEndAnchor(node) {}

    visitWordBoundary(node) {}

    visitNonWordBoundary(node) {}

    visitLookahead(node) {}

    visitNegativeLookahead(node) {}

    // atoms
    visitCharacter(node) {}

    visitSet(node) {}

    visitGroup(node) {}

    visitGroupBackReference(node) {}

    visitQuantifier(node) {}
}

const myVisitor = new MyRegExpVisitor()
myVisitor.visit(regExpAst)
// extract visit results from the visitor state.

Compatibility

This library is written in ES5 style and is compatiable with all major browsers and modern node.js versions.

TODO / Limitations