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chevrotain

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chevrotain is an open source library created in 2015.

#569on PLDB 9Years Old
Download source code:
git clone https://github.com/SAP/chevrotain

Parser Building Toolkit for JavaScript


Example from the web:
"use strict" /** * An Example of implementing a CSV Grammar with Chevrotain. * * Based on: https://github.com/antlr/grammars-v4/blob/master/csv/CSV.g4 * * Note that this is a pure grammar without any actions (either embedded or via a CST Visitor). */ const { createToken, Lexer, Parser, EMPTY_ALT } = require("chevrotain") // ----------------- lexer ----------------- const Text = createToken({ name: "Text", pattern: /[^,\n\r"]+/ }) const Comma = createToken({ name: "Comma", pattern: /,/ }) const NewLine = createToken({ name: "NewLine", pattern: /\r?\n/ }) const String = createToken({ name: "String", pattern: /"(?:""|[^"])*"/ }) const allTokens = [Text, String, Comma, NewLine] const CsvLexer = new Lexer(allTokens) // Parser class CsvParser extends Parser { constructor() { super(allTokens) // not mandatory, using $ (or any other sign) to reduce verbosity const $ = this $.RULE("csvFile", () => { $.SUBRULE($.hdr) $.AT_LEAST_ONE(() => { $.SUBRULE2($.row) }) }) $.RULE("hdr", () => { $.SUBRULE($.row) }) $.RULE("row", () => { $.SUBRULE($.field) $.MANY(() => { $.CONSUME(Comma) $.SUBRULE2($.field) }) $.CONSUME(NewLine) }) $.RULE("field", () => { $.OR([ { ALT: () => $.CONSUME(Text) }, { ALT: () => $.CONSUME(String) }, { ALT: EMPTY_ALT("empty field") } ]) }) // very important to call this after all the rules have been defined. // otherwise the parser may not work correctly as it will lack information // derived during the self analysis phase. this.performSelfAnalysis() } } // wrapping it all together // reuse the same parser instance. const parser = new CsvParser([]) module.exports = function(text) { // 1. Tokenize the input. const lexResult = CsvLexer.tokenize(text) // 2. Set the Parser's input parser.input = lexResult.tokens // 3. invoke the desired parser rule const cst = parser.csvFile() return { cst: cst, lexResult: lexResult, parseErrors: parser.errors } }

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