Options API vs Composition API decision in Vue

Introduction

Vue offers two ways to write components: Options API and Composition API. Choosing between them helps you organize your code better and work more easily.

You want simple and clear code for small projects or beginners.

You need to reuse logic across components in a clean way.

You want better TypeScript support and more flexible code structure.

You are working on a large project with complex components.

You want to gradually migrate old Vue code to newer patterns.

Syntax

Vue

Options API:
export default {
  data() {
    return { count: 0 };
  },
  methods: {
    increment() {
      this.count++;
    }
  }
}

Composition API:
import { ref } from 'vue';
export default {
  setup() {
    const count = ref(0);
    function increment() {
      count.value++;
    }
    return { count, increment };
  }
}

The Options API groups code by options like data, methods, and computed.

The Composition API groups code by feature or logic using functions inside setup().

Examples

Options API example: data and methods are separate sections.

Vue

export default {
  data() {
    return { message: 'Hello' };
  },
  methods: {
    greet() {
      alert(this.message);
    }
  }
}

Composition API example: data and methods are together inside setup().

Vue

import { ref } from 'vue';
export default {
  setup() {
    const message = ref('Hello');
    function greet() {
      alert(message.value);
    }
    return { message, greet };
  }
}

Sample Program

This is a simple Vue component using the Composition API. It shows a count and a button to increase it. The count updates reactively when you click the button.

Vue

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

<script setup>
import { ref } from 'vue';
const count = ref(0);
function increment() {
  count.value++;
}
</script>

Important Notes

The Options API is easier for beginners and small projects.

The Composition API is better for complex logic and code reuse.

You can mix both APIs in the same project if needed.

Summary

The Options API organizes code by options like data and methods.

The Composition API organizes code by logical features inside setup().

Choose based on project size, complexity, and your comfort with Vue.

Practice

1. Which Vue API organizes component code by options like data, methods, and computed?

easy

A. Options API

B. Composition API

C. Both APIs organize code this way

D. Neither API uses options

Solution

1. Step 1: Understand Options API structure

   The Options API groups code by options such as data, methods, and computed.

2. Step 2: Compare with Composition API

   The Composition API organizes code inside the setup() function by logical features, not by options.

3. Final Answer:

   Options API -> Option A

4. Quick Check:

   Options API groups by options like data and methods [OK]

Hint: Options API groups by options, Composition API uses setup() [OK]

Common Mistakes:

• Confusing Composition API with Options API structure
• Thinking both APIs organize code the same way
• Believing Options API uses setup() function

2. Which of the following is the correct way to declare a reactive state variable using the Composition API in Vue?

easy

A. const count = ref(0); inside setup()

B. data() { return { count: 0 } }

C. methods: { count() { return 0 } }

D. computed: { count: () => 0 }

Solution

1. Step 1: Identify Composition API reactive declaration

   In Composition API, reactive state uses ref() inside setup(), e.g., const count = ref(0);.

2. Step 2: Compare other options

   data() { return { count: 0 } } is Options API syntax, A and D are for methods and computed properties, not reactive refs.

3. Final Answer:

   const count = ref(0); inside setup() -> Option A

4. Quick Check:

   Use ref() in setup() for reactive state [OK]

Hint: Use ref() inside setup() for reactive state in Composition API [OK]

Common Mistakes:

• Using data() syntax in Composition API
• Confusing methods with reactive state
• Trying to declare reactive state outside setup()

3. Given this Vue component using Composition API:

import { ref } from 'vue';
export default {
  setup() {
    const count = ref(0);
    function increment() {
      count.value++;
    }
    return { count, increment };
  }
}

What will be the value of count after calling increment() twice?

medium

A. 0

B. 1

C. 2

D. undefined

Solution

1. Step 1: Understand ref and increment function

   count is a ref initialized to 0. Calling increment() increases count.value by 1 each time.

2. Step 2: Calculate count after two increments

   Starting at 0, after two increments: 0 + 1 + 1 = 2.

3. Final Answer:

   2 -> Option C

4. Quick Check:

   Two increments add 2 to count.value [OK]

Hint: ref.value changes with increments; count.value++ twice = 2 [OK]

Common Mistakes:

• Forgetting to use .value with ref
• Assuming count is a plain number, not a ref
• Thinking increment does not change count

4. Identify the error in this Vue component using Options API:

export default {
  data() {
    count: 0
  },
  methods: {
    increment() {
      this.count++;
    }
  }
}

medium

A. Incorrect method name increment

B. data() should be a property, not a function

C. Using this.count instead of count

D. Missing return statement in data()

Solution

1. Step 1: Check data() function syntax

   In Options API, data() must return an object. Here, it lacks return keyword.

2. Step 2: Verify other parts

   Method name and usage of this.count are correct. data() is correctly a function.

3. Final Answer:

   Missing return statement in data() -> Option D

4. Quick Check:

   data() must return an object [OK]

Hint: data() must return an object with return keyword [OK]

Common Mistakes:

• Omitting return in data()
• Confusing this.count with count
• Thinking data() can be an object directly

5. You have a large Vue project with many components sharing logic like fetching data and handling loading states. Which API choice is best and why?

hard

A. Options API, because it separates code by options making it easier to read

B. Composition API, because it groups related logic together for better reuse

C. Options API, because it requires less code and is more modern

D. Composition API, because it avoids using setup() and is simpler

Solution

1. Step 1: Consider project size and logic reuse

   Large projects with shared logic benefit from grouping related code together for reuse and clarity.

2. Step 2: Compare API strengths

   Composition API allows grouping logic inside setup(), making reuse easier. Options API separates by options, which can scatter related logic.

3. Final Answer:

   Composition API, because it groups related logic together for better reuse -> Option B

4. Quick Check:

   Composition API groups logic for reuse in large projects [OK]

Hint: Use Composition API for reusable logic in big projects [OK]

Common Mistakes:

• Choosing Options API for better reuse in large projects
• Thinking Composition API avoids setup()
• Believing Options API is more modern