let normalize = str => {
  let result = {}
  let c
  
  // 字符串转化为数组
  let arr = str.split(/[\[\]]/g).filter(Boolean)
  
  // 生成结构化数据
  arr.forEach((item, index) => {
    if(index != 0) {
      c.children = {}
      c.children.value = item
      c= c.children
    } else {
      result.value = item
      c= result
    }
  })
  
  return result
}
let str = '[abc[bcd[def]]]'
normalize(str)
// {value: 'abc', children: {value: 'bcd', children: {value: 'def'}}}