编辑代码

const tree = {
  val: 'a',
  children: [
    {
      val: 'b',
      children: [
        {
          val: 'd',
          children: []
        },
        {
          val: 'e',
          children: []
        }
      ]
    },
    {
      val: 'c',
      children: [
        {
          val: 'f',
          children: []
        },
        {
          val: 'g',
          children: []
        }
      ]
    }
  ]
}

function dfs (root) {
    console.log('+++：', root.val)

    root.children.forEach(dfs)
    console.log(root.val)
}
dfs(tree)