Changes in Vue3 compared to Vue2: Better TypeScript type inference

Vue is a popular JavaScript framework for building user interfaces. Vue3 is the latest version of the Vue framework, with a lot of improvements and optimizations based on Vue2. One of them is improvements in TypeScript type inference. This article will introduce the improvements in type inference in Vue3 and illustrate them through code examples.

In Vue2, we need to manually declare properties such as Props and Methods for Vue components, and manually add type annotations to these properties. In Vue3, we can use the new Composition API to define the logic of components more naturally and let TypeScript automatically deduce types behind the scenes.

The following is a simple code example showing better type inference in Vue3.

import { defineComponent, ref } from 'vue';

const HelloWorld = defineComponent({
  props: {
    name: String, // Vue2中需要手動添加類型注解
    age: Number,
  },
  setup(props) {
    const count = ref(0); // Vue2中也需要手動添加類型注解

    const increaseCount = () => {
      count.value++; // Vue2中需要手動添加類型注解
    };

    return {
      count,
      increaseCount,
    };
  },
  template: `
    <div>
      <h1>Hello, {{ name }}!</h1>
      <p>You are {{ age }} years old.</p>
      <button @click="increaseCount">Click me</button>
      <p>Count: {{ count }}</p>
    </div>
  `,
});

export default HelloWorld;

In the above example, we define a Vue component through defineComponent. In the props attribute, we directly specify the types String and Number for the name and age properties, while No need to manually add type annotations. Similarly, in the setup function, we use the ref function to create a responsive count variable without manually adding type annotations. Finally, in templates, we can also use these properties and variables directly.

When we write Vue3 components using TypeScript, it will automatically deduce these types and provide related type checking. This means we can catch potential type errors earlier in the development process and reduce the likelihood of runtime errors.

In addition to better type inference, Vue3 also introduces some other features, such as reactive and computed, for the definition and use of reactive data and computed properties. Also friendlier.

In summary, Vue3’s improvements in type inference compared to Vue2 allow developers to define components more naturally and get more type checks with less work. This helps us a lot in writing maintainable and robust Vue applications.

It should be noted that although Vue3 provides these improvements, type derivation still needs to be used carefully in actual development, and type annotations are added to key properties and variables in a timely manner to ensure code quality and maintainability. .

(Note: The code example in this article uses the syntax of Vue3.0.0 version, which may be changed in future versions. Please check the official documentation carefully when writing code.)

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