Implementing a Custom onUpdated Hook in Vue with TypeScript

Vue 3 introduced the onUpdated lifecycle hook, which allows you to run code after a component has been re-rendered. This challenge asks you to implement a simplified version of this hook using Vue's reactivity system and the watch function, ensuring type safety with TypeScript. This exercise will solidify your understanding of Vue's reactivity and how to leverage it to observe and react to component updates.

Problem Description

You need to create a generic useOnUpdated composable function that mimics the behavior of Vue's built-in onUpdated hook. This composable should accept a callback function as an argument and register it to be executed after the component updates. The callback should receive the updated component instance as its argument. The composable should handle component unmounting gracefully to prevent memory leaks.

Key Requirements:

• Generic Type: The composable should be generic, allowing it to work with any component type.
• Callback Execution: The provided callback function must be executed after each component update.
• Component Instance Argument: The callback function should receive the component instance as its first argument.
• Unmounting Handling: The composable must properly unregister the watcher when the component is unmounted to avoid memory leaks.
• TypeScript Safety: The code must be written in TypeScript and provide type safety for the callback function and component instance.

Expected Behavior:

When the useOnUpdated composable is called within a Vue component's setup function, it should register a watcher that observes the component's reactivity. Whenever a reactive property changes and triggers a re-render, the provided callback function should be executed with the updated component instance. When the component is unmounted, the watcher should be automatically removed.

Edge Cases to Consider:

• Component Unmounting: Ensure the watcher is removed when the component is unmounted to prevent errors and memory leaks.
• Multiple Updates: The callback should be executed for every update, not just the first one.
• Reactive Property Changes: The watcher should react to any changes in reactive properties within the component.

Examples

Example 1:

Input: A Vue component with a reactive property 'count' and a callback function that logs the updated count.
Output: The callback function is logged to the console after each update of the 'count' property.
Explanation: The `useOnUpdated` composable registers a watcher that observes the component's reactivity. When 'count' changes, the callback is executed, logging the new value.

Example 2:

Input: A Vue component that is unmounted before the 'count' property is updated.
Output: No error is thrown, and the callback function is not executed.
Explanation: The `useOnUpdated` composable automatically removes the watcher when the component is unmounted, preventing errors and unnecessary executions.

Example 3: (Complex Scenario)

Input: A Vue component with multiple reactive properties and a callback function that updates another reactive property based on the updated values.
Output: The callback function correctly updates the other reactive property after each update of the component's properties.
Explanation: The watcher observes all reactive properties, and the callback function executes after each update, allowing for complex interactions between reactive properties.

Constraints

• The composable must be implemented using Vue 3's reactivity system and the watch function.
• The composable must be generic and type-safe.
• The callback function must receive the component instance as its argument.
• The composable must handle component unmounting gracefully.
• The solution should be concise and readable.
• The composable should not rely on external libraries.

Notes

• Consider using getCurrentInstance() to access the component instance within the watcher.
• Remember to use onUnmounted to remove the watcher when the component is unmounted.
• Think about how to handle potential errors within the callback function. While not explicitly required, robust error handling is a good practice.
• Focus on creating a reusable and type-safe composable that accurately mimics the behavior of Vue's onUpdated hook.