102 lines
3.0 KiB
Markdown
102 lines
3.0 KiB
Markdown
[](https://badge.fury.io/js/regexp-to-ast)
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[](https://circleci.com/gh/bd82/regexp-to-ast)
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[](https://coveralls.io/github/bd82/regexp-to-ast?branch=master) [](https://greenkeeper.io/)
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# regexp-to-ast
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Reads a JavaScript Regular Expression **literal**(text) and outputs an Abstract Syntax Tree.
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## Installation
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- npm
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```
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npm install regexp-to-ast
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```
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- Browser
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```
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<script src="https://unpkg.com/regexp-to-ast/lib/parser.js"></script>
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```
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## API
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The [API](https://github.com/bd82/regexp-to-ast/blob/master/api.d.ts) is defined as a TypeScript definition file.
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## Usage
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- Parsing to an AST:
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```javascript
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const RegExpParser = require("regexp-to-ast").RegExpParser
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const regexpParser = new RegExpParser.parser()
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// from a regexp text
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const astOutput = regexpParser.pattern("/a|b|c/g")
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// text from regexp instance.
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const input2 = /a|b/.toString()
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// The same parser instance can be reused
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const anotherAstOutput = regexpParser.pattern(input2)
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```
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- Visiting the AST:
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```javascript
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// parse to an AST as before.
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const { RegExpParser, BaseRegExpVisitor } = require("regexp-to-ast")
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const regexpParser = new RegExpParser.parser()
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const regExpAst = regexpParser.pattern("/a|b|c/g")
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// Override the visitor methods to add your logic.
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class MyRegExpVisitor extends BaseRegExpVisitor {
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visitPattern(node) {}
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visitFlags(node) {}
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visitDisjunction(node) {}
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visitAlternative(node) {}
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// Assertion
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visitStartAnchor(node) {}
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visitEndAnchor(node) {}
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visitWordBoundary(node) {}
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visitNonWordBoundary(node) {}
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visitLookahead(node) {}
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visitNegativeLookahead(node) {}
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// atoms
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visitCharacter(node) {}
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visitSet(node) {}
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visitGroup(node) {}
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visitGroupBackReference(node) {}
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visitQuantifier(node) {}
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}
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const myVisitor = new MyRegExpVisitor()
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myVisitor.visit(regExpAst)
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// extract visit results from the visitor state.
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```
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## Compatibility
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This library is written in ES**5** style and is compatiable with all major browsers and **modern** node.js versions.
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## TODO / Limitations
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- Use polyFill for [string.prototype.at](https://github.com/mathiasbynens/String.prototype.at)
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to support unicode characters outside BMP.
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- Descriptive error messages.
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- Position information in error messages.
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- Support unicode flag escapes.
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- Ensure edge cases described in ["The madness of parsing real world JavaScript regexps"](https://hackernoon.com/the-madness-of-parsing-real-world-javascript-regexps-d9ee336df983) are supported.
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- Support deprecated octal escapes
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