feat: add list to tree

Author: chachaxw

js/list_to_tree.js

@@ -0,0 +1,95 @@
+/*
+ * @Author: Chacha
+ * @Date: 2022-05-09 23:13:53
+ * @Last Modified by: Chacha
+ * @Last Modified time: 2022-05-09 23:15:09
+ */
+
+/**
+ *
+    let arr = [
+        {id: 1, name: '部门1', pid: 0},
+        {id: 2, name: '部门2', pid: 1},
+        {id: 3, name: '部门3', pid: 1},
+        {id: 4, name: '部门4', pid: 3},
+        {id: 5, name: '部门5', pid: 4},
+    ]
+  =>
+    [
+        {
+            "id": 1,
+            "name": "部门1",
+            "pid": 0,
+            "children": [
+                {
+                    "id": 2,
+                    "name": "部门2",
+                    "pid": 1,
+                    "children": []
+                },
+                {
+                    "id": 3,
+                    "name": "部门3",
+                    "pid": 1,
+                    "children": [
+                        // 结果 ,,,
+                    ]
+                }
+            ]
+        }
+    ]
+ *
+ *
+ */
+// 非递归版本
+const arrayToTree = (array) => {
+    const hashMap = {};
+    let result = [];
+
+    array.forEach((it) => {
+        const { id, pid } = it;
+
+        // 不存在时，先声明children树形
+        // 这一步也有可能在下面出现
+        if (!hashMap[id]) {
+            hashMap[id] = {
+                children: [],
+            };
+        }
+
+        hashMap[id] = {
+            ...it,
+            children: hashMap[id].children,
+        };
+        // 处理当前的item
+        const treeIt = hashMap[id];
+
+        // 根节点，直接push
+        if (pid === 0) {
+            result.push(treeIt);
+        } else {
+            // 也有可能当前节点的父父节点还没有加入hashMap，所以需要单独处理一下
+            if (!hashMap[pid]) {
+                hashMap[pid] = {
+                    children: [],
+                };
+            }
+            // 非根节点的话，找到父节点，把自己塞到父节点的children中即可
+            hashMap[pid].children.push(treeIt);
+        }
+    });
+
+    return result;
+};
+
+const data = [
+    // 注意这里，专门把pid为1的元素放一个在前面
+    { id: 2, name: "部门2", pid: 1 },
+    { id: 1, name: "部门1", pid: 0 },
+    { id: 3, name: "部门3", pid: 1 },
+    { id: 4, name: "部门4", pid: 3 },
+    { id: 5, name: "部门5", pid: 4 },
+    { id: 7, name: "部门7", pid: 6 },
+];
+
+console.log(JSON.stringify(arrayToTree(data), null, 2));