递归评论

学习于：https://www.bilibili.com/video/BV1vT4y137So?p=33

<script>
    let comment = [
      { comment_id: 1, user_id: 43, comment_date: "04-23", comment_content: "蜡笔小新很好看!", parent_id: null },
      { comment_id: 2, user_id: 19, comment_date: "04-24", comment_content: "还不错哦!很好看", parent_id: null },
      { comment_id: 3, user_id: 17, comment_date: "04-25", comment_content: "我也感觉蜡笔小新很好看", parent_id: "1" },
      { comment_id: 4, user_id: 14, comment_date: "04-26", comment_content: "我感觉机器猫更好看一点", parent_id: "3" },
      { comment_id: 5, user_id: 13, comment_date: "04-27", comment_content: "好看,已三连!", parent_id: null },
      { comment_id: 6, user_id: 21, comment_date: "04-26", comment_content: "你是机器猫的粉丝吗", parent_id: "4" },
      { comment_id: 7, user_id: 14, comment_date: "04-27", comment_content: "是的,我是机器猫的粉丝", parent_id: "6" },
      { comment_id: 8, user_id: 23, comment_date: "04-27", comment_content: "我更喜欢白嫖!", parent_id: "5" },
      { comment_id: 9, user_id: 25, comment_date: "04-28", comment_content: "你个白嫖怪", parent_id: "8" }
    ]

    // 方式一： for循环方式生成子评论
    let list = []
    for (let i = 0; i < comment.length; i++) {
      // 一级评论
      if (comment[i].parent_id == null) {
        list.push(comment[i])

        // 二级评论
        for (let j = 0; j < comment.length; j++) {
          if (comment[i].comment_id == comment[j].parent_id) {
            comment[i].children = [comment[j]]

            // 三级评论
            for (let k = 0; k < comment.length; k++) {
              if (comment[j].comment_id == comment[k].parent_id) {
                comment[j].children = [comment[k]]
              }
            }
          }
        }
      }
    }
    console.log(list)

    // 方式二： 递归方式生成子评论
    function fn(temp) {
      let list = []
      for (let i = 0; i < comment.length; i++) {
        if (comment[i].parent_id == temp) {
          list.push(comment[i]) // 筛选后生成的父级评论
          comment[i].children = fn(comment[i].comment_id)
        }
      }
      return list
    }
    const res = fn(null)
    console.log(res)
  </script>