The difference between Vue3 and Vue2: the introduction of combined API

The difference between Vue3 and Vue2: the introduction of combined API

With the continuous development of front-end technology, Vue.js as a powerful front-end framework is also constantly evolving. As a popular version, Vue2 has a simple and easy-to-use API and a flexible responsive system, and has been used to develop many excellent applications. However, in order to further improve the ease of use and maintainability of Vue, Vue3 introduces a new combined API, which is in sharp contrast to the Options API of Vue2.

The core concept of the combined API is to divide the logic within the component according to functions, and combine these logics through a new mechanism (setup() function). This approach makes the component's code clearer, more reusable, and more convenient for unit testing.

First, let us look at a sample component written using Vue2:

<template>
  <div>
    <h1 id="title">{{ title }}</h1>
    <button @click="increaseCount">Increase</button>
    <p>Count: {{ count }}</p>
  </div>
</template>

<script>
export default {
  data() {
    return {
      title: 'Vue2 Counter',
      count: 0
    }
  },
  methods: {
    increaseCount() {
      this.count++
    }
  }
}
</script>

In Vue2, we use the data attribute to define the responsive data of the component, and Define the component's methods in methods.

Now, let’s rewrite this example component using Vue3’s composition API:

<template>
  <div>
    <h1 id="title">{{ title }}</h1>
    <button @click="increaseCount">Increase</button>
    <p>Count: {{ count }}</p>
  </div>
</template>

<script>
import { reactive, ref } from 'vue'

export default {
  setup() {
    const title = 'Vue3 Counter'
    const count = ref(0)

    function increaseCount() {
      count.value++
    }

    return {
      title,
      count,
      increaseCount
    }
  }
}
</script>

In Vue3, we use the setup() function to combine the logic of the component . In the setup() function, we use the ref function to define the count variable, and the reactive function to define the title Variables, ensure they are all responsive. At the same time, we also expose the increaseCount methods and use them in the template.

By using the combined API, we can combine the logic of components more flexibly. For example, we can define multiple ref objects and reactive objects and then use them in the setup() function. We can also use other Vue APIs, such as computed and watch, to enhance the functionality of the component.

To summarize, Vue3’s combined API brings many benefits. It makes components clearer, more reusable, and improves code maintainability. At the same time, the combined API is also more convenient for unit testing, because we can directly test the logic defined in the setup() function. However, it should be noted that since the combined API is a new feature of Vue3 and is incompatible with the Options API of Vue2, the code needs to be refactored when migrating old Vue2 projects to Vue3.

I hope that through the introduction of this article, you will have a deeper understanding of Vue3's combined API and be able to better apply it in actual projects. Let us look forward to the future development of Vue.js!

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