Lexical Parser (lexical-parser)

About

Reads and tokenizes an input string given a set of string or regex patterns.

Purpose

With this module you are able to parse a string like "int a = 5" into this:

Token{name: 'int',lexeme: 'int',position: 0}Token{name: 'id',lexeme: 'a',position: 4}Token{name: '=',lexeme: '=',position: 6}Token{name: 'integer',lexeme: '5',position: 8}

Installing

Install this module in your project by running:

$ npm install --save lexical-parser

Example usage

'use strict';constLex=require('lexical-parser')letinput='block { int a = 0 int b = 3 if (a < b && b > a) { print("Hello World") } }'// You can specify an exact string or a regex for the tokenlettokenMatchers=['block','if','{','}','(',')','<','>','=','&&','int',['integer',/[0-9]+/],['id',/[a-zA-Z][a-zA-Z0-9]*/],['string',/\".*?\"/]]// The pattern to ignore in the inputletignorePattern='[\n\s \t]+'letlex=newLex(input,tokenMatchers,ignorePattern)lettoken=undefinedtry{do{token=lex.nextToken()console.log(token)}while(token)}catch(err){// Error handlingif(err.code==="LEXICAL_ERROR"){console.log(`\n${err.message}\n`)console.log(`Position: ${err.position}`)console.log(`Character: ${err.character}`)console.log(`Nearby code: ${err.nearbyCode}`)}elseconsole.log(err)}

Output

Token{name: 'block',lexeme: 'block',position: 0}Token{name: '{',lexeme: '{',position: 6}Token{name: 'int',lexeme: 'int',position: 8}Token{name: 'id',lexeme: 'a',position: 12}Token{name: '=',lexeme: '=',position: 14}Token{name: 'integer',lexeme: '0',position: 16}Token{name: 'int',lexeme: 'int',position: 18}Token{name: 'id',lexeme: 'b',position: 22}Token{name: '=',lexeme: '=',position: 24}Token{name: 'integer',lexeme: '3',position: 26}Token{name: 'if',lexeme: 'if',position: 28}Token{name: '(',lexeme: '(',position: 31}Token{name: 'id',lexeme: 'a',position: 32}Token{name: '<',lexeme: '<',position: 34}Token{name: 'id',lexeme: 'b',position: 36}Token{name: '&&',lexeme: '&&',position: 38}Token{name: 'id',lexeme: 'b',position: 41}Token{name: '>',lexeme: '>',position: 43}Token{name: 'id',lexeme: 'a',position: 45}Token{name: ')',lexeme: ')',position: 46}Token{name: '{',lexeme: '{',position: 48}Token{name: 'id',lexeme: 'print',position: 50}Token{name: '(',lexeme: '(',position: 55}Token{name: 'string',lexeme: '"Hello World"',position: 56}Token{name: ')',lexeme: ')',position: 69}Token{name: '}',lexeme: '}',position: 71}Token{name: '}',lexeme: '}',position: 73}undefined