What is Vue.js Composition API

Introduction

The Vue Composition API is a new feature introduced in Vue 3 that provides a set of functions for composing component logic in a more flexible and reusable manner. It allows developers to organize and reuse code more effectively, especially for complex components or scenarios where the options API may lead to code duplication or complex component structures.

Key features and concepts of the Composition API

1. Function-based Composition: Instead of defining component options (data, computed properties, methods, etc.) within a single object, as in the options API, you can organize your component logic into reusable functions.
2. Composition Functions: These are functions that encapsulate specific areas of concern within a component, such as data manipulation, computed properties, methods, lifecycle hooks, or even custom logic. Composition functions can be composed together to build complex component behavior.
3. Reactive Data: The Composition API still leverages Vue's reactivity system, allowing you to create reactive data, computed properties, and watch effects within composition functions.
4. Lifecycle Hooks: You can define lifecycle logic using composition functions such as onMounted, onUpdated, and onUnmounted, which replaces the traditional lifecycle hooks in the options API.
5. Composition Utilities: Vue provides a set of built-in composition utilities, such as ref, reactive, computed, watch, and watchEffect to work with reactive data and side effects.
6. Global Mixins and Plugins: The Composition API simplifies the use of global mixins and plugins, allowing you to encapsulate shared logic and extend components in a more modular way.

Composition API offers several benefits:

• Improved Code Organization: Composition functions allow you to organize code based on features or concerns, leading to cleaner and more maintainable code.
• Code Reusability: With the Composition API, you can easily reuse logic across components, reducing duplication and improving code sharing.
• Better TypeScript Support: The Composition API provides better TypeScript support, allowing for stronger type inference and easier type checking.

Usage of the Composition API in a Vue 3 component

Here's a simple example demonstrating the usage of the Composition API in a Vue 3 component:

<template>
  <div>
    <p>Counter: {{ counter }}</p>
    <button @click="increment">Increment</button>
  </div>
</template>

<script>
import { ref } from 'vue';

export default {
  setup() {
    // Define reactive state
    const counter = ref(0);

    // Define a method
    function increment() {
      counter.value++;
    }

    // Return reactive state and methods
    return {
      counter,
      increment
    };
  }
}
</script>

In this example, the setup function defines reactive state (counter) and a method (increment) using composition functions (ref). The state and method are then returned from the setup function, making them accessible in the component's template.

Summary

Overall, the Vue Composition API offers several benefits, including improved code organization, enhanced code reuse, and better TypeScript support. By leveraging function-based composition and reactive data, developers can build more maintainable and scalable Vue.js applications with ease