将扁平化的 JSON 数据转换为嵌套结构的 JSON

function buildNestedStructure(data) {
  const topLevelItems = []; // 存储顶级节点
  const itemMap = {}; // 存储每个层级的最后一个节点，用于快速查找父节点

  for (const item of data) {
    const { title, metaData } = item;
    const newItem = { title, metaData };

    if (metaData.level === 1) {
      // 如果是顶级节点，直接添加到 topLevelItems
      topLevelItems.push(newItem);
    } else {
      // 否则，找到父节点并添加到其 subNav 属性中
      const parentLevel = metaData.level - 1;
      const parentItem = itemMap[parentLevel];

      if (!parentItem.subNav) {
        parentItem.subNav = [];
      }

      parentItem.subNav.push(newItem);
    }

    // 将当前节点添加到 itemMap 中，以便后续节点可以找到它作为父节点
    itemMap[metaData.level] = newItem;
  }

  return topLevelItems;
}

// 示例数据
const content = [
  { title: "Item 1", metaData: { "level": 1, "desc": "Some Desc 1", "displayOnOverview": true }},
  { title: "Item 2", metaData: { "level": 2, "desc": "Some Desc 2", "displayOnOverview": true }},
  { title: "Item 3", metaData: { "level": 2, "desc": "Some Desc 3", "displayOnOverview": false }},
  { title: "Item 4", metaData: { "level": 3, "desc": "Some Desc 4", "displayOnOverview": true }},
  { title: "Item 5", metaData: { "level": 1, "desc": "Some Desc 5", "displayOnOverview": true }}
];


// 调用函数并打印结果
const output = buildNestedStructure(content);
console.log(JSON.stringify(output, null, 2));