vue.js数组中有多个子级，怎么把他们全部拼接到单个数组同一级中

[
    {
      "id": 1,
      "title": "1",
      "children": [
        {
          "id": 2,
          "title": "1.1",
        },
        {
          "id": 3,
          "title": "1.2",
        },
        {
          "id": 4,
          "title": "1.3",
          "children": [],
        },
        {
          "id": 5,
          "title": "1.4",
					"children": [
            {
              "id": 6,
          		"title": "1.4.1",
              "children": [],
            },
              {
              "id": 7,
          		"title": "1.4.2",
            }
          ],
        },
        {
          "id": 8,
          "title": "1.5",
        }
      ]
    },
    {
      "id": 2,
      "title": "2",
      "children": [],
    }
  ],

 item.children.length > 0改为item.children && item.children.length > 0即可，仅判断item.children.length > 0可能会存在item.children不存在，导致item.children.length报错undifined。基本就是雨生百谷老铁的代码 

export function FlatArray (data) {
  console.log('原数组长度：', data.length)
  if (data.length === 0) {
    return []
  }
  let arr = []
  data.map((item) => {
    if (item.children && item.children.length > 0) {
      arr = arr.concat(FlatArray(item.children))
    } else {
      item.children = []
    }
    arr.push(item)
  })
  console.log('打平后数组长度：', arr.length)
  return arr
}

就是给拉平呗

 //扁平化数组（tree）变为一维数组
      FlatArray = (data, val) => {
            if (data.length == 0) {
                  return [];
            }
            let arr = [];
            console.log(data,"00")
            data.map((item) => {
                  
                  if (item.children.length > 0) {
                        arr = arr.concat(this.FlatArray(item.children));
                  }else{
                        item.children=[]
                  }
                  arr.push(item);
            })
            return arr;
      }
      let data = [
            {
                  "id": 1,
                  "title": "1",
                  "children": [
                        {
                              "id": 2,
                              "title": "1.1",
                              "children": [],
                        },
                        {
                              "id": 3,
                              "title": "1.2",
                              "children": [],
                        },
                        {
                              "id": 4,
                              "title": "1.3",
                              "children": [],
                        },
                        {
                              "id": 5,
                              "title": "1.4",
                              "children": [
                                    {
                                          "id": 6,
                                          "title": "1.4.1",
                                          "children": [],
                                    },
                                    {
                                          "id": 7,
                                          "title": "1.4.2",
                                          "children": [],
                                    }
                              ],
                        },
                        {
                              "id": 8,
                              "title": "1.5",
                              "children": [],
                        }
                  ]
            },
            {
                  "id": 2,
                  "title": "2",
                  "children": [],
            }
      ]
      //调用
      console.log(FlatArray(data))

let data = [{
    "id": 1,
    "title": "1",
    "children": [{
        "id": 2,
        "title": "1.1",
      },
      {
        "id": 3,
        "title": "1.2",
      },
      {
        "id": 4,
        "title": "1.3",
        "children": [],
      },
      {
        "id": 5,
        "title": "1.4",
        "children": [{
            "id": 6,
            "title": "1.4.1",
            "children": [],
          },
          {
            "id": 7,
            "title": "1.4.2",
          }
        ],
      },
      {
        "id": 8,
        "title": "1.5",
      }
    ]
  },
  {
    "id": 2,
    "title": "2",
    "children": [],
  }
]

let newarr = [];

function levelTreePro(arr, newarr) {
  arr.forEach(item => {
    if (item.children && item.children.length > 0) {

      newarr.push({
        id: item.id,
        title: item.title
      })
      levelTree(item.children, newarr)
    } else {
      newarr.push({
        id: item.id,
        title: item.title
      })
    }
  })
};

levelTreePro(data, newarr);
console.log(newarr) //平级结果 

let LevelArr= []
function levelTree(arr, newarr) {
                arr.forEach(item => {
                    if (item.children && item.children.length > 0) {
                        newarr.push(item)
                        levelTree(item.children, newarr)
                    } else {
                        newarr.push(item)
                    }
                })
            }
  levelTree(data, LevelArr)

用递归