# 树和对象转换

给定一棵树

const tree = [
  {
    title: '1',
    id: '1',
    children: [
      {
        title: '2-1',
        id: '2-1',
        children: [
          {
            title: '2-1-1',
            id: '2-1-1',
          },
        ],
      },
      {
        title: '2-2',
        id: '2-2',
      },
    ],
  },
]

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# 树转一维数组

function treeTransArray(tree, parentId) {
  return tree.reduce(
    (arr, { children = [], ...item }) =>
      arr.concat(
        [{ ...item, parentId }],
        treeTransArray(children, item.id)
      ),
    []
  )
}

const arr = treeTransArray(tree, '0')
console.log(arr)

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树转一维数组

# 一维数组转树

function arrayTransTree(list, key){
  const tree = list.filter((parent) => {
    const branchArr = list.filter((child) => {
      return parent.id === child[key]
    })

    parent.children = []
    if (branchArr.length > 0) {
      parent.children = branchArr
    }
    const flag = parent[key] === '0'
    return flag
  })
  return tree
}

const arr = treeTransArray(tree, '0')
console.log(arrayTransTree(arr, 'parentId'))

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# 树转对象

查找父类包括自己所在的对象

function makeRevMap(list, parents) {
  return list.reduce((result, item) => {
    result[item.id] = parents.concat(item)
    if (
      item.children &&
      Array.isArray(item.children) &&
      item.children.length > 0
    ) {
      result = { ...result, ...makeRevMap(item.children, result[item.id]) }
    }
    return result
  }, {})
}
console.log(makeRevMap(a, []))

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树转对象

# 树平铺

  function treeToList(treeRoot) {
    const arr = []

    function loop(tree, tmpArr) {
      tree.forEach(element => {
        const childArr = tmpArr.concat([{ title: element.title }])
        if (element.children) {
          loop(element.children, childArr, arr)
        } else {
          arr.push(childArr)
        }
      });
    }
    loop(treeRoot, [])
    return arr
  }
  console.log(treeToList(tree))

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← 斐波那列