regexp-to-ast

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

Installation

- npm
``
npm install regexp-to-ast
`
- Browser
`

`

API

The API is defined as a TypeScript definition file.

Usage

- Parsing to an AST:

`javascript
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:

`javascript
// 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

- Use polyFill for string.prototype.at
to support unicode characters outside BMP.
- Descriptive error messages.
- Position information in error messages.
- Support unicode flag escapes.
- Ensure edge cases described in "The madness of parsing real world JavaScript regexps" are supported.
- Support deprecated octal escapes