A parser for tree syntax

tree-compiler.js

// const input =
//  '(2 (7 (2 () ()) (6 (5 () ()) (11 () ()))) (5 () (9 (4 () ()) ())))'

const tokenizer = input => {
  let current = 0
  const tokens = []

  while (current < input.length) {
    let char = input[current]

    if (char === '(' || char === ')') {
      tokens.push({
        type: 'paren',
        value: char,
      })
      current += 1
      continue
    }

    const WHITESPACE = /\s/
    if (WHITESPACE.test(char)) {
      current += 1
      continue
    }

    const NUMBERS = /[0-9]/
    if (NUMBERS.test(char)) {
      let value = ''
      while (NUMBERS.test(char)) {
        value += char
        current += 1
        char = input[current]
      }

      tokens.push({
        type: 'number',
        value: +value,
      })

      continue
    }

    throw new Error(`Invalid Syntax: ${char} at ${current}`)
  }

  return tokens
}

const parseNode = tokens => {
  let token = tokens.shift()
  console.log(token, tokens)

  if (token.type === 'number') {
    return token.value
  }

  if (token.type === 'paren' && token.value === '(') {
    if (tokens[0].type === 'paren' && tokens[0].value === ')') {
      tokens.shift()
      return null
    }

    const node = {
      element: parseNode(tokens),
      left: parseNode(tokens),
      right: parseNode(tokens),
    }

    tokens.shift()
    return node
  }
}


// console.log(parseNode(tokenizer(input))