const values = [1, [2, 3, [4], 5], 6]
const keys = '[a, [b, c, [d], e], f]'

function parse (keys, values) {
  const isArrayReg = /^\[(.+)]$/
  const keyMatchReg = /(.*?)([\[|,\]])(.*)/
  const arrayMatch = keys.match(isArrayReg)
  if (!arrayMatch) return {}

  let depth = 0
  let index = 0
  const deepIndexMap = new Map()
  const deepValueMap = new Map()

  const result = {}
  let content = arrayMatch[1]
  deepIndexMap.set(depth, index)
  deepValueMap.set(depth, values)

  while (content) {
    const keyMatch = content.match(keyMatchReg)
    if (!keyMatch) {
      result[content] = values[index]
      content = ''
      continue
    }

    const key = keyMatch[1].trim()
    if (key !== '') {
      result[key] = values[index]
      index++
    }

    const splitChar = keyMatch[2]
    if (splitChar === '[') {
      values = values[index]
      deepIndexMap.set(depth, index)
      depth++
      index = 0
      deepIndexMap.set(depth, index)
      deepValueMap.set(depth, values)
    }
    if (splitChar === ']') {
      depth--
      index = deepIndexMap.get(depth) + 1
      values = deepValueMap.get(depth)
      deepIndexMap.delete(depth)
      deepValueMap.delete(depth)
    }
    content = keyMatch[3].trim()
  }

  return result
}

const result = parse(keys, values)
console.log(result)