A simple data format built on Jevko

easyjevko.js

// run this script with
//
//     node --experimental-network-imports easyjevko.js
//
// on Node.js or
//
//     deno run --allow-net easyjevko.js
//
// on Deno

import("https://cdn.jsdelivr.net/gh/jevko/parsejevko.js@v0.1.6/mod.js").then(({parseJevko}) => {
  const v = parseJevko(`
hello [world] 
list [[1][2][3]]
  `)
  
  console.log(toValue(v))
  // this should print
  // Map { "hello" => "world", "list" => [ "1", "2", "3" ] }
})

const fromValue = (value) => {
  if (typeof value === 'string') {
    let suffix = ''
    for (const c of value) {
      if (c === open || c === close || c === escape) suffix += escape
      suffix += c
    }
    return {subjevkos: [], suffix}
  }
  if (value instanceof Map) {
    const subjevkos = []
    if (value.size === 0) throw Error(`Empty Map not allowed`)
    else if (value.has('')) throw Error(`Empty key not allowed`)
    else for (const [k, v] of value) {
      if (typeof k !== 'string') throw Error(`Nonstring keys not allowed`)
      subjevkos.push({prefix: k, jevko: fromValue(v)})
    }
    return {subjevkos, suffix: ''}
  }
  if (Array.isArray(value)) {
    const subjevkos = []
    if (value.length === 0) throw Error(`Empty Array not allowed`)
    else for (const v of value) {
      subjevkos.push({prefix: '', jevko: fromValue(v)})
    }
    return {subjevkos, suffix: ''}
  }
  throw Error(`Unrecognized value: ${value}`)
}

const toValue = (jevko) => {
  const {subjevkos, suffix} = jevko

  if (subjevkos.length === 0) return suffix

  if (suffix.trim() !== '') throw Error('nonempty suffix')

  const {prefix} = subjevkos[0]

  if (prefix.trim() === '') {
    const ret = []

    for (const {prefix, jevko} of subjevkos) {
      if (prefix.trim() !== '') throw Error('nonempty prefix')
      ret.push(toValue(jevko))
    }
  
    return ret
  }

  const ret = new Map()

  for (const {prefix, jevko} of subjevkos) {
    const key = prefix.trim()
    if (ret.has(key)) throw Error(`key ${key} duplicated!`)
    ret.set(key, toValue(jevko))
  }

  return ret
}