数组 & 树

数组转树

function arrToTree(arr) {
  const map = new Map()
  for (const item of arr) {
    map.set(item.id, item)
  }

  const roots = []
  for (const item of arr) {
    if (item.parent === null) {
      roots.push(item)
    } else {
      const parent = map.get(item.parent)
      if (!parent.children) {
        parent.children = []
      }
      parent.children.push(item)
    }
  }

  return roots
}

// --- 测试
const tree = arrToTree([
  { id: 1, value: 1, parent: null },
  { id: 2, value: 2, parent: 1 },
  { id: 3, value: 3, parent: 2 },
  { id: 4, value: 4, parent: 1 },
])
console.log(tree)
// --- 测试

树转数组

function treeToArr(tree, parent = null, result = []) {
  for (const node of tree) {
    const { children, ...rest } = node
    const flatNode = { ...rest, parent }
    result.push(flatNode)
    if (children && Array.isArray(children)) {
      treeToArr(children, node.id, result)
    }
  }
  return result
}

// --- 测试
const arr = treeToArr([
  {
    id: 1,
    value: 1,
    parent: null,
    children: [
      {
        id: 2,
        value: 2,
        parent: 1,
        children: [
          {
            id: 3,
            value: 3,
            parent: 2,
          },
        ],
      },
      {
        id: 4,
        value: 4,
        parent: 1,
      },
    ],
  },
])
console.log(arr)
// --- 测试