lex-parser

0.1.4 verified Sat Apr 25 auth: no javascript maintenance

A parser for lexical grammars used by jison and jison-lex. Currently at version 0.1.4, it parses lexical grammar definitions (similar to those used by Lex/Yacc) and returns a JSON representation. It is a low-level dependency for jison tools and not commonly used directly. The package appears to be stable but rarely updated, with the last release likely years ago. Unlike higher-level alternatives like jison itself, lex-parser focuses solely on parsing the grammar syntax.

Common errors

error lexParser.parse is not a function ↓

cause Incorrect import: using import or require improperly. For example, importing as default but using .parse as if it were a method on an object.

fix

Use either: const result = lexParser.parse('%%...'); if lexParser is the default import (CommonJS), or const { parse } = require('lex-parser'); result = parse('%%...');

error Cannot find module 'lex-parser' ↓

cause Package not installed.

fix

Install via npm: npm install lex-parser

Warnings

gotcha Package uses CommonJS module format by default; ESM may require additional configuration. ↓

fix Use dynamic import or configure bundler for CommonJS compatibility.

deprecated Package is rarely updated; consider using jison-lex directly for grammar parsing inside jison workflows. ↓

fix Instead of using lex-parser directly, rely on jison or jison-lex which include it as a dependency.

gotcha The parse function expects a complete grammar string with '%%' separator between rules and code; missing it results in invalid output. ↓

fix Ensure grammar string includes '%%' to separate the rules section from optional trailing code.

Install

npm install lex-parser

yarn add lex-parser

pnpm add lex-parser

Imports

default (parse function)
wrong
```
const lexParser = require('lex-parser'); // Works for CJS but not ESM
```
correct
```
import lexParser from 'lex-parser'; const result = lexParser.parse('%%...');
```
Package exposes a single parse function as default export. In CommonJS environments, require is acceptable; for ESM, use import.

parse function (named)

wrong

import { lexParser } from 'lex-parser'; // Wrong symbol; named export is 'parse', not 'lexParser'.

correct

import { parse } from 'lex-parser'; const result = parse('%%...');

The named export 'parse' is available. Avoid confusing with the package name.

Quickstart

Shows how to install, import, and use lexParser.parse() to parse a simple lexical grammar and output JSON.

import lexParser from 'lex-parser';

const grammar = `
NAME [a-zA-Z_][a-zA-Z0-9_-]*
%%
{NAME} return 'NAME';
`;

const parsed = lexParser.parse(grammar);
console.log(JSON.stringify(parsed, null, 2));