What is the Composition API in Vue.js ?

The Composition API in Vue.js is a new set of APIs introduced in Vue.js 3, providing a more flexible and logical approach to organizing component code. This contrasts with the Options API in Vue 2, which requires developers to organize different aspects of a component (such as data, methods, and lifecycle hooks) into separate option objects.

Key Features

1. Better Logic Reuse and Code Organization

The Composition API enables developers to more naturally extract and reuse code logic. By leveraging the new setup() function, developers can combine related features logically rather than by option type, making functional modularization and reuse easier.

Example: Suppose we have a component for fetching and displaying user data. With the Composition API, we can group all user-related logic together:

javascript
import { ref, onMounted } from 'vue';

export default {
  setup() {
    const userData = ref(null);

    const fetchUserData = async () => {
      userData.value = await fetch('/api/user').then(res => res.json());
    };

    onMounted(() => {
      fetchUserData();
    });

    return {
      userData
    };
  }
}

2. Improved Type Inference

For TypeScript projects, the Composition API enhances type inference quality and consistency through tighter integration.

3. More Intuitive Debugging

Since related functional logic can now be combined together, this makes debugging more intuitive.

Use Cases

• Large Projects: For complex and large Vue applications, the Composition API's modularization and code organization capabilities help developers manage code more effectively.
• Reusing Logic: When sharing logic across multiple components, the Composition API simplifies logic extraction and reuse through custom hooks (e.g., useUser).
• Using TypeScript: TypeScript users benefit from better support from the Composition API.

Overall, the Composition API is a powerful new feature in Vue.js, offering developers greater flexibility and control, especially when handling complex components and logic reuse.