Vue's Composition API: A Tale of Two States (Pros and Cons)
Tags: vue3, composition
Published: 2023-07-25 12:42:38

## Introduction

Vue's Composition API is a new way of structuring Vue components that was introduced in Vue 3. It provides a way to group related code together using the setup() function, which can make it easier to reason about your code and reduce the likelihood of introducing bugs. In this article, we'll take a detailed look at the pros and cons of using the Composition API in Vue, with examples to illustrate each point.

## The Pros
### Better code organization
One of the biggest advantages of using the Composition API is that it encourages better code organization. With the setup() function, you can group related code together based on its functionality, rather than its type. This can make it easier to navigate and maintain your codebase, especially as it grows in complexity.

For example, consider a component that needs to fetch data from an API, store it in a data property, and display it in a template. With the Options API, you would need to define a data property, a method to fetch the data, and a computed property to display it. With the Composition API, you can group all of this functionality together in the setup() function:
```
import { ref, onMounted } from 'vue'

export default {
  setup() {
    const data = ref(null)

    const fetchData = async () => {
      const response = await fetch('https://api.example.com/data')
      data.value = await response.json()
    }

    onMounted(fetchData)

    return { data }
  }
}
```
### Composing complex logic:
Another benefit of the Composition API is that it makes it easier to compose complex logic in your components. Instead of relying on a mix of data properties, computed properties, and methods, you can now group related code together using the setup() function. This can make your code more readable and reduce the likelihood of introducing bugs.

For example, consider a component that needs to fetch data from an API, filter it based on user input, and display the results in a template. With the Options API, you would need to define multiple data properties, a method to fetch the data, a computed property to filter it, and another computed property to display it. With the Composition API, you can group all of this functionality together in the setup() function:
```
import { ref, computed, onMounted } from 'vue'

export default {
  setup() {
    const data = ref(null)
    const filterTerm = ref('')

    const fetchData = async () => {
      const response = await fetch('https://api.example.com/data')
      data.value = await response.json()
    }

    onMounted(fetchData)

    const filteredData = computed(() => {
      if (data.value) {
        return data.value.filter(item => item.name.includes(filterTerm.value))
      } else {
        return []
      }
    })

    return { filterTerm, filteredData }
  }
}
```
## The Cons
### More difficult to learn
One of the biggest drawbacks of the Composition API is that it can be more difficult to learn than the Options API. The new syntax and concepts can take some time to get used to, and there's a bit of a learning curve involved. However, once you get the hang of it, the Composition API can be a powerful tool in your Vue.js arsenal.

For example, consider the same component we defined earlier using the Options API:
```
export default {
  data() {
    return {
      data: null,
      filterTerm: ''
    }
  },

  async mounted() {
    const response = await fetch('https://api.example.com/data')
    this.data = await response.json()
  },

  computed: {
    filteredData() {
      if (this.data) {
        return this.data.filter(item => item.name.includes(this.filterTerm))
      } else {
        return []
      }
    }
  }
}
```
### Overkill for simple components
Another potential downside of the Composition API is that it can sometimes feel like overkill for simple components. If you're just building a simple button or input field, you may not need the full power of the Composition API. In these cases, using the Options API (the traditional way of defining Vue components) may be more appropriate.

For example, consider a simple component that just displays a message:
```
// Using the Options API
export default {
  data() {
    return {
      message: 'Hello, world!'
    }
  }
}

// Using the Composition API
import { ref } from 'vue'

export default {
  setup() {
    const message = ref('Hello, world!')
    return { message }
  }
}
```
## Conclusion
In conclusion, the Composition API is a powerful new feature in Vue.js that can help you write cleaner, more organized code. While it may not be the right choice for every component, it's definitely worth taking the time to learn and experiment with. Whether you're composing a symphony of code or just mixing itup with Vue, the Composition API can provide a lot of benefits for your Vue.js projects. Just keep in mind that there may be a learning curve involved, and that it may not be necessary for every component you build. With that said, the Composition API can be a valuable tool in your Vue.js toolbox, and it's definitely worth considering for your next project.