ParseRiver

A monadic parser library for TypeScript and JavaScript

Get Started

Just run:

npm install parseriver

Your first parser

You can combine simple built-in parsers using a wide variety of built-in combinators and achieve powerful results with human readable code.

import {
  str,
  oneOf,
  separatedBy,
  surroundeByExtract,
} from 'parseriver'

const parser = surroundedByExtract(str('['), str(']'))(
  separatedBy(str(','))(
    oneOf(
      str('Yes'),
      str('No')
    )
  )
)

console.log(
  parser.run('[Yes,No,No,No,Yes]')
)

Say hi to $do notation

Now you don't need haskell to effectively and comfortably pipe parsers.

import {
  $do,
  str,
  letters,
  whitespace,
  optionalWhitespace,
} from 'parseriver'

const parser = $do(function* () {
  yield optionalWhitespace
  yield str('I')
  yield whitespace
  yield str('am')
  yield whitespace

  const name = yield letters
  yield whitespace
  const surname = yield letters

  return { name, surname }
})

console.log(
  parser.run('   I   am  John         Galt')
)

Can it get more human-readable?

Use recursion for more power

JavaScript's eager evaluation makes it more difficult to build self-referential parsers. With recursive it's easier than ever.

import {
  recursive,
  oneOf,
  str,
  decimalFloat,
  Parser,
} from 'parseriver'

const parser: Parser<number> = recursive(() => oneOf(
  decimalFloat,
  surroundedByExtract(str('('), str(')'))(parser)
))

console.log(
  parser.run('(((-17.032)))')
)