client - add services

client/app/services/category.service.ts

@@ -0,0 +1,18 @@
+import { cloneDeep } from 'lodash';
+import axios from '../axios/axios';
+import { CategoryModel } from '../model';
+
+export class CategoryService {
+  private static categoryCache: CategoryModel[];
+
+  public static async getCategories(): Promise<CategoryModel[]> {
+    // return cache if it exists
+    if (CategoryService.categoryCache) {
+      return Promise.resolve(cloneDeep(CategoryService.categoryCache));
+    }
+
+    const res = await axios.get('/api/category');
+    CategoryService.categoryCache = cloneDeep(res.data.data);
+    return res.data.data;
+  }
+}