feat(tree): add tree building utility

Author: honghuangdc

src/index.ts

@@ -1,5 +1,6 @@
 export * from './common';
 export * from './string';
 export * from './storage';
+export * from './tree';
 
 export type * from './types';

src/tree.ts

@@ -0,0 +1,38 @@
+type BaseNode<K extends string, P extends string> = {
+  [key in K]: string | number;
+} & {
+  [key in P]?: string | number | null;
+};
+
+type BaseTreeNode<K extends string, P extends string, T extends BaseNode<K, P>> = T & {
+  children?: Array<BaseTreeNode<K, P, T>>;
+};
+
+export const buildTree = <K extends string, P extends string, T extends BaseNode<K, P>>(
+  flatNodes: T[],
+  key: K,
+  parentKey: P
+) => {
+  const map = new Map<string | number, BaseNode<K, P>>();
+  const tree: Array<BaseTreeNode<K, P, T>> = [];
+
+  for (const node of flatNodes) {
+    const current = (map.get(node[key]) || { ...node }) as BaseTreeNode<K, P, T>;
+    Object.assign(current, node);
+    map.set(node[key], current);
+
+    if (node[parentKey] === null || node[parentKey] === undefined) {
+      tree.push(current);
+    } else {
+      const parent = (map.get(node[parentKey]) || { ...current, [key]: node[parentKey] }) as BaseTreeNode<K, P, T>;
+
+      if (!parent.children) {
+        parent.children = [];
+      }
+      parent.children.push(current);
+      map.set(node[parentKey], parent);
+    }
+  }
+
+  return tree;
+};