README

@carlosvpi/parser

A ~6kB Parsing utility

Install

npm install @carlosvpi/parser

yarn add @carlosvpi/parser

Parse a string

Import the parser

const getParser = require('@carlosvpi/parser')

import getParser from '@carlosvpi/parser'

Use the parser

const grammar = `
  S = 's' A | '0';
  A = 'a' S;
`
const parser = getParser(grammar)

parser is a hash. Each rule head of the grammar is a key in the hash. In this case,

typeof parser.S === 'function'
typeof parser.A === 'function'

If the string head is the head of a rule, and input is some string, then

parser[head](input)

parses the input using the given grammar, using the head as an axiom. The output of parser[head](input) is a parsed tree.

The grammar

The grammar that the getParser function (from @carlosvpi/parser) takes is a string that follows the same syntax described in the Wikipedia page for EBNF.

The tree

The result of parser[head](input) is a tree where nodes have this shape:

[root, ...children]

The root is a string with these possible values:

'$LITERAL': has only one child, the parsed literal,
'$MATCH': its children are the result of applying a regex to the input using js regex match,
'$CONCAT': its children are other nodes,
head: this node corresponds to the parsing the input using a rule head

Example

This code

parser(`
  S = 's' A | '0';
  A = 'a' S;
`).S('sasa0')

produces this tree:

[
   "S",
   [
      "$CONCAT",
      [
         "$LITERAL",
         "s"
      ],
      [
         "A",
         [
            "$CONCAT",
            [
               "$LITERAL",
               "a"
            ],
            [
               "S",
               [
                  "$CONCAT",
                  [
                     "$LITERAL",
                     "s"
                  ],
                  [
                     "A",
                     [
                        "$CONCAT",
                        [
                           "$LITERAL",
                           "a"
                        ],
                        [
                           "S",
                           [
                              "$CONCAT",
                              [
                                 "$LITERAL",
                                 "0"
                              ]
                           ]
                        ]
                     ]
                  ]
               ]
            ]
         ]
      ]
   ]
]

Usage no npm install needed!