javascript - 另一个 promise 中的 promise

Question

我有一个 promise ，可以为每个部门获取其类别，我必须为每个类别添加另一个级别以获取其子类别。

我添加了另一个 promise ，我只是想知道这是否是正确的方法，请告知。

componentDidMount = async () => {
    const departments = await getDepartments();
    const departmentsWithcategories = await Promise.all(
      departments.map(async department => {
        const categories = await getCategories(department.id);
        categories.map(async category => {
          const subCategories = await getSubCategories(category.id);
          return { ...categories, subCategories };
        });
        return { ...department, categories };
      }),
    );
    this.setState({ departmentsWithcategories });
  };

更改前的功能:

componentDidMount = async () => {
    const departments = await getDepartments();
    const departmentsWithcategories = await Promise.all(
      departments.map(async department => {
        const categories = await getCategories(department.id);
        return { ...department, categories };
      }),
    );
    this.setState({ departmentsWithcategories });
  };

Answer 1

您还需要另一个 Promise.all 来等待内部循环的结果。此外，您还忽略了它的返回值，并且可能您打算传播单个category而不是categories数组。

async componentDidMount() {
    const departments = await getDepartments();
    const departmentsWithCategories = await Promise.all(departments.map(async department => {
        const categories = await getCategories(department.id);
        const categoriesWithSubcategories = Promise.all(categories.map(async category => {
//            ^^^^^^^^^^^^^^^^^^^^^^^^^^^   ^^^^^^^^^^^
            const subCategories = await getSubCategories(category.id);
            return { ...catgory, subCategories };
//                      ^^^^^^^
        }));
        return { ...department, categories: categoriesWithSubcategories };
//                                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    }));
    this.setState({ departmentsWithCategories });
}