What is the Difference Between Composition API and Options API in VueJS

In web development, the choice of framework and tools is crucial for the structure, scalability, and maintenance of a project. Two strategies stand out when we talk about Vue.js: the Options API and the Composition API. Both provide different ways to organize and manage the logic of an application, each with its own benefits and specific use cases.

Options API: The Essence of Vue

The Options API is the traditional way of using Vue.js. Present since the beginning, its syntax is based on an options object to structure the properties of a component.

It may seem complicated, but in practice, it's simpler than it seems!

Here's how it looks:

<template>
  <div>
    <p>Count: {{ count }}</p>
    <br />
    <button v-on:click="increment">Increment</button>
    <button v-on:click="reset">Reset</button>
  </div>
</template>

<script>
export default {
  // Component state
  data() {
    return {
      count: 0
    };
  },

  // Component methods
  methods: {
    increment() {
      this.count++;
    },
    reset() {
      this.count = 0;
    }
  },

  // Computed property
  computed: {
    doubleCount() {
      return this.count * 2;
    }
  }
};
</script>

Structure:

• data: Defines the reactive data of the component, i.e., where the variables that will have dynamic values are declared.
• methods: Where we specify custom functions. These functions can change states, react to user events, and perform specific logic.
• computed: Defines computed properties that derive from data, i.e., values that only need to be calculated once and updated only when a related variable changes.

Vue.js also has other options, such as name, components, props, directives, watch, and emits, among others. However, we can explore these aspects further in a future article.

Let's examine some of the properties and limitations presented by the Options API:

• Access to data through this: Variables defined in the data property can only be accessed through the this. context, as illustrated in the increment and reset methods.
• Rigid code division: Functions and variables are categorized into specific sections, such as data, methods, computed. This can split the logic associated with similar functionality, making it harder to read and maintain the code in larger-scale projects.
• Difficulties in reusing logic: The Options API uses Mixins to share logic between components, which can result in naming conflicts and issues in code traceability.

Composition API: Flexibility and Practicality

The Composition API is the new way to structure code, introduced in Vue 3. With the Composition API, you can structure your component's logic in a more transparent and intuitive way.

Let's see how much has really changed and clarify any doubts about the Composition API.

I'll create the same application, but this time with the Composition API. Observe how it looks:

<template>
  <div>
    <p>Count: {{ count }}</p>
    <br />
    <button v-on:click="increment">Increment</button>
    <button v-on:click="reset">Reset</button>
  </div>
</template>

<script setup>
import { ref, computed } from "vue";

// Reactive state
const count = ref(0);

// Methods
function increment() {
  count.value++;
}

function reset() {
  count.value = 0;
}

// Computed property
const doubleCount = computed(() => count.value * 2);
</script>

Structure:

• <script setup/>: Where all the logic and code that will not be rendered to the user is placed.
• ref(): Defines whether a variable will be reactive or not.
• computed(): Performs the same function as the computed in the Options API.

Let's explore some of the functionalities brought by the Composition API:

• It is necessary to import what we are going to use.
• We need to use the ref() method to make the variable reactive. For example, if count did not have ref(), when updated, it would not update automatically and would require a page reload.
• The data of variables that use ref() can only be accessed using .value, as used in the increment and reset functions.

Below is a gif of the application we created in this article with Vue.js:

Detailed Comparison

Each API in Vue.js has unique characteristics that affect how the code is organized, managed, and interpreted. The choice between Options API and Composition API mainly impacts code structuring and readability. Below, we highlight the main differences between them:

But when to use each API?

The Options API is ideal for:

• More structured and declarative code - Ideal for those who prefer a clear distinction between state, methods, and computed properties (such as data, methods, computed, etc.).
• Easy learning - If you are starting with Vue.js, this methodology is more intuitive and organized, following a clearly established pattern.
• Compatibility with older libraries - Some Vue libraries still rely on the Options API, making this option more practical to prevent compatibility issues.
• Simplified debugging - Due to the fixed structure of the code, it becomes easier to understand the flow and identify failures, especially for those accustomed to Vue.js's conventional architecture.
• Effective resource use in smaller projects - In smaller-scale applications, the Options API provides a straightforward and efficient solution, free of extra complexity.

The Composition API is more recommended for:

• Greater adaptability and code reuse - Through Functions, we can share logic between components without the limitations of Mixins in the Options API.
• Improved organization in large projects - Instead of segmenting code by options (data, methods, etc.), logic can be grouped by functionality, simplifying maintenance.
• Advanced reactivity management - By using ref(), you gain more control over the state.
• Ease in creating custom hooks - The Composition API allows the creation of reusable hooks, making the structure more modular and simplifying code maintenance.
• Enhanced experience with TypeScript - If you plan to use TypeScript in your project, the Composition API integrates more smoothly, providing more precise typing and improved support for type inference.

Final Considerations

Now that you know the differences between the Options API and the Composition API, you are ready to choose the best option for your project. Remember that each has its advantages and disadvantages, and everything depends on the complexity of your project.

However, when it comes to personal preference, I generally prefer using the Composition API in my personal projects, due to its optimization with TypeScript and the ability to group logic.

Regardless of the API chosen, Vue.js remains a powerful and flexible tool for Front-End development. 🚀