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

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

Current Tags

0.5.0 ... latest (5 years ago)