Implementing Asynchronous Data Fetching in Vue 3 Composition API

This challenge focuses on leveraging the power of the Composition API in Vue 3 to gracefully handle asynchronous operations within the setup function. You will build a component that fetches data from an external API when it's initialized and displays it to the user, while also providing a clear loading state and handling potential errors. This is a fundamental pattern for building modern, interactive web applications.

Problem Description

You need to create a Vue 3 component using TypeScript that fetches a list of "users" from a mock API endpoint. The data fetching process should occur asynchronously within the setup function.

Key Requirements:

• Asynchronous Data Fetching: Implement a mechanism to fetch data from https://jsonplaceholder.typicode.com/users when the component is mounted.
• Loading State: Display a "Loading..." message to the user while the data is being fetched.
• Error Handling: If an error occurs during the data fetching process, display an informative error message to the user.
• Data Display: Once the data is successfully fetched, display a list of user names.
• Reactivity: Ensure that the loading state, error message, and fetched data are reactive and update the UI accordingly.

Expected Behavior:

1. When the component is first rendered, the UI should show "Loading...".
2. If the API call is successful, the "Loading..." message should disappear, and a list of user names (e.g., "John Doe", "Jane Smith") should be displayed.
3. If the API call fails (e.g., network error, invalid URL), the "Loading..." message should disappear, and an error message like "Error fetching users." should be displayed.

Edge Cases:

• Consider what happens if the API returns an empty array of users. The component should gracefully handle this by displaying a message like "No users found." instead of an empty list.

Examples

Example 1:

Scenario: Successful data fetch.

Input: (Implicitly, the component is mounted and calls the API)

Output (rendered in UI):

Loading...

(After a short delay)

User List:
- Leanne Graham
- Ervin Howell
- Clementine Bauch
- ... (rest of the user names)

Explanation: The component initiates the fetch, displays "Loading...", and upon successful retrieval of user data from the API, it updates the UI to show the list of names.

Example 2:

Scenario: API request fails.

Input: (Implicitly, the component is mounted and calls the API, but the API returns an error or is unreachable)

Output (rendered in UI):

Loading...

(After a short delay)

Error fetching users.

Explanation: The component attempts to fetch data, shows "Loading...", but encounters an error. It then displays an error message.

Example 3:

Scenario: API returns an empty user list.

Input: (Implicitly, the component is mounted and calls the API, and the API returns [])

Output (rendered in UI):

Loading...

(After a short delay)

No users found.

Explanation: The API call succeeds but returns no user data. The component handles this by displaying a "No users found" message.

Constraints

• The API endpoint https://jsonplaceholder.typicode.com/users must be used.
• The solution must be implemented using Vue 3 and TypeScript.
• The setup function should be used for data fetching and state management.
• Avoid using external state management libraries like Pinia or Vuex for this challenge.
• The solution should be efficient and not perform unnecessary re-renders.

Notes

• You can use fetch API or a library like axios for making HTTP requests. Choose one and stick with it for consistency.
• The onMounted lifecycle hook is a good place to initiate asynchronous operations in setup.
• Remember to handle loading and error states reactively using ref or reactive from Vue.
• Consider how you will manage the asynchronous nature of the fetch operation to avoid race conditions or updating the UI with stale data.
• Think about how to represent the user data (e.g., define an interface for a User object).