上一篇文章中提到，当将嵌套数据存储在Algolia中时，您需要将它们扁平化为平面结构，以便可以搜索和过滤它们。因此，Algolia Hierarchy concept有助于您将嵌套对象转换为平面结构，并使其可搜索和分类。

假设您有以下数据：

const departments = [
 { name: "Marketing", id: 1, hierarchy: "" },
 { name: "Sales", id: 2, hierarchy: "" },
 { name: "Design", id: 3, hierarchy: "" },
 { name: "SEO", id: 4, hierarchy: "1" },
 { name: "Social Media", id: 5, hierarchy: "1" },
 { name: "PPC", id: 6, hierarchy: "2" },
 { name: "Web Design", id: 7, hierarchy: "3" },
 { name: "Graphic Design", id: 8, hierarchy: "3" },
 { name: "HTML", id: 9, hierarchy: "7" },
 { name: "CSS", id: 10, hierarchy: "7" },
 { name: "Logos", id: 11, hierarchy: "8" },
 { name: "Posters", id: 12, hierarchy: "8" },
 { name: "Typography", id: 13, hierarchy: "8" },
];

在以上数据中，每个部门项目都有一个ID、一个名称和一个等级制度字段(hierarchy field)。 hierarchy field就是用于组织 Algolia hierarchy 的字段，值为父级ID。 通过以下代码示例，使用Algolia Hierarchy来将此层次结构数据扁平：

function flattenDepartments(departments, parent) {
  const flatDepartments = [];

  for (const department of departments) {
    if (department.hierarchy === parent) {
      flatDepartments.push(department);

      const children = flattenDepartments(departments, department.id);
      flatDepartments.push(...children);
    }
  }

  return flatDepartments;
}

const flatDepartments = flattenDepartments(departments, "");
console.log(flatDepartments);

在 flattenDepartments 函数中，我们查找具有给定父级ID的所有子部门，并对他们进行递归。然后，将所有子项目添加到 flatDepartments 数组中，并在递归函数完成时返回结果。

使用这个函数，您可以