SOURCE

let tree = [
    {
        id: 1, title: "1", children: [
            { id: 2, title: "1-1" },
            { id: 3, title: "1-2", children: [{ id: 4, title: "1-2-1", children: [{ id: 5, tile: "1-2-1-1" }] }] },
            { id: 6, title: "1-3", children: [{ id: 7, title: "1-3-1" }] },
        ]
    },
    { id: 8, title: '2' },
    { id: 9, title: '3', children: [{ id: 10, title: '3-1' }] }
]

/**
 * 树结构转扁平结构
 * @param data
 * @return {Array}
 */
function transformTreeToFlat(data) {
    const cloneData = JSON.parse(JSON.stringify(data))
    let result = []
    function fn(array) {
        for (let i of array) {
            result.push(i)
            if (i.children && i.children.length !== 0) {
                fn(i.children)
                delete i.children
            }
        }
    }
    fn(cloneData)
    return result
}

console.log(transformTreeToFlat(tree))

const list = [{ id: 1, name: '司令', pid: 0 }, { id: 2, name: '军长', pid: 1 }, { id: 3, name: '副军长', pid: 1 }, { id: 4, name: '旅长', pid: 3 }, { id: 5, name: '团长', pid: 4 },]
/**
 * 扁平结构转树结构
 * @param data
 * @return {*} 含children的树形结构
 */
function transformFlatToTree(data) {
    const cloneData = JSON.parse(JSON.stringify(data))
    function getTreeList(rootList, pid, list) {
        // 初始化第一层节点
        for (let item of rootList) {
            if (item.pid === pid) {
                list.push(item)
            }
        }
        // 递归子节点
        for (let i of list) {
            i.children = []
            getTreeList(rootList, i.id, i.children)
            if (i.children.length === 0) {
                delete i.children
            }
        }
        return list
    }
    return getTreeList(cloneData, 0, [])
}
console.log(transformFlatToTree(list))

function arrToTree(list) {
    // 定义最终需要返回的树形结构数据    
    let treeData = []
    // 对传入的数组进行遍历    
    list.forEach(item => {
        // 如果pid没有值,那就是顶级对象,直接添加进数组        
        if (!item.pid) { treeData.push(item) }
        // 理解为二次遍历 ：每个对象都找一遍自己的孩子添加到children       
        let objList = list.filter(data => data.pid === item.id)
        if (objList.length) { item.children = objList }
    })
    return treeData
}
console.log(arrToTree(list));

/**
 * 根据index删除节点
 * @param arr 树形tableList数据
 * @param index 所在tableList
 */
function deleteNodeByIndex(arr, index) {
  let count = 0
  let returnFlag = false
  function fn(arr) {
    for (let i = 0; i < arr.length; i++) {
      if (returnFlag) {
        // 终止递归
        return
      }
      if (count === index) {
        arr.splice(i, 1)
        returnFlag = true
        return
      }
      count++
      if (arr[i].children && arr[i].children.length !== 0) {
        fn(arr[i].children)
      }
    }
  }
  fn(arr)
}