js 给树形(层级)数组添加层级标识

树形数据，需要给每层的数据添加层级，如下：

const treeData = [
  {
    id: 1, name: 'a', children: [
      { id: 101, name: 'a1', children: null }
    ]
  },
  {
    id: 2, name: 'b', children: [
      {
        id: 201, name: 'b1', children: [
          { id: 211, name: 'b2', children: null }
        ]
      }
    ]
  },
]

const arrayTreeAddLevel = (array, levelName = 'level', childrenName = 'children') => {
  if (!Array.isArray(array)) return []
    const recursive = (array, level = 0) => {
    level++
    return array.map(v => {
      v[levelName] = level
      const child = v[childrenName]
      if (child && child.length) recursive(child, level)
        return v
      })
    }
  return recursive(array)
}

const newData = arrayTreeAddLevel(treeData)