从父子id的原始数据创建Json层次结构

[
  { "id": 1, "parent_id": null },
  { "id": 2, "parent_id": 1 },
  { "id": 3, "parent_id": 1 },
  { "id": 4, "parent_id": 2 },
  { "id": 5, "parent_id": 2 },
  { "id": 6, "parent_id": 3 },
  { "id": 7, "parent_id": 3 }
]

let jsonHierarchy = {};

for (let i = 0; i < rawData.length; i++) {
  let node = rawData[i];
  let nodeId = node.id;
  let parentNodeId = node.parent_id;

  // Check if parent node exists in the hierarchy
  if (jsonHierarchy[parentNodeId]) {
    // Parent node exists, add current node as its child
    if (!jsonHierarchy[parentNodeId].children) {
      jsonHierarchy[parentNodeId].children = [];
    }
    jsonHierarchy[parentNodeId].children.push(node);
  } else {
    // Parent node does not exist, add current node as root
    jsonHierarchy[nodeId] = node;
  }
}

let jsonHierarchyString = JSON.stringify(jsonHierarchy);
console.log(jsonHierarchyString);