/*
 * 傳入的陣列有id和父節點pid欄位，通過它們的關聯構造成一棵或多棵樹結構
 * @param nodes 集合
 * @param treeRootId 根節點的id
 */
function createTreeData(nodes, treeRootId) {
    var groups = {};
    // 按父節點將節點分組
    for (var i in nodes) {
        if (!groups[nodes[i].pid]) {
            groups[nodes[i].pid] = [];
        }
        groups[nodes[i].pid].push(nodes[i]);
        if
 
 (treeRootPid && treeRootPid === nodes[i].id) { // 發現傳入的根節點id作為節點id時，將根節點設定為該節點的父節點
            treeRootPid = nodes[i].pid;
        }
    }

    var rootNodes = groups[treeRootPid];
    groups[treeRootPid] = null; // [SAFEGUARD]防止自為父節點或互為父節點（有環圖結構）導致的死迴圈
    function traverseTreeNodeGroup(treeNodeGroup) {
        for
 
 (var i in treeNodeGroup) {
            var node = treeNodeGroup[i];
            if (groups[node.id]) {
                node.children = groups[node.id];
                groups[node.id] = null; // [SAFEGUARD]防止自為父節點或互為父節點（有環圖結構）導致的死迴圈
                traverseTreeNodeGroup(node.children);
            }
        }
    }
    traverseTreeNodeGroup(rootNodes);
    return
 
 rootNodes;
}

// 測試陣列
var nodes = [
    {id: '01', pid: '0'},
    {id: '02', pid: '0'},
    {id: '011', pid: '01'},
    {id: '012', pid: '01'},
    {id: '021', pid: '02'},
    {id: '022', pid: '02'},
    {id: '0221', pid: '022'},
    {id: '0222', pid: '022'}
];
// 呼叫
createTreeData(nodes, '0');
/* 返回如下結構
[
    {
        "id": "01",
        "pid": "0",
        "children": [
            {
                "id": "011",
                "pid": "01"
            },
            {
                "id": "012",
                "pid": "01"
            }
        ]
    },
    {
        "id": "02",
        "pid": "0",
        "children": [
            {
                "id": "021",
                "pid": "02"
            },
            {
                "id": "022",
                "pid": "02",
                "children": [
                    {
                        "id": "0221",
                        "pid": "022"
                    },
                    {
                        "id": "0222",
                        "pid": "022"
                    }
                ]
            }
        ]
    }
]
*/