Detailed explanation of the render function in Vue3: Master the custom rendering of Vue3 components

Detailed explanation of the render function in Vue3: Mastering custom rendering Vue3 components

Vue3 is the latest version of the Vue framework, bringing many exciting new features and functions, one of which is the render function Redesigned and upgraded. The render function in Vue3 can not only customize the rendering method of Vue3 components, but also better support TypeScript and Composition API. This article will introduce the render function in Vue3 in detail to help readers become proficient in custom rendering Vue3 components.

What is the render function?

In Vue, template is the main way to create component templates. But in fact, template is just syntactic sugar, and is compiled into a render function internally. Therefore, the render function is the most basic rendering function of the Vue component, and its main function is to render the component into a DOM node.

The render function in Vue3 is slightly different from that in Vue2. It no longer receives the h function as the first parameter, but directly returns a VNode (virtual node), which means that we do not need to separate Introduce h function. For example:

// Vue2中的render函数
render: function (h) {
  return h('div', 'hello world')
}

// Vue3中的render函数
render: function () {
  return h('div', 'hello world')
}

The parameter received by the render function in Vue3 is still a context object (ctx). This context object contains all properties and methods of the current component instance, such as props, data, methods, etc. However, in Vue3, we can use ES6's destructuring syntax to simplify the code:

render({props, data, slots, attrs, emit}) {
   // ...
}

When using the render function, we need to explicitly declare it in the component options. For example:

export default {
  render() {
    return h('div', 'hello world')
  }
}

Render function syntax and usage

In Vue3, we can use the render function to create component templates, and we can also use JSX syntax to simplify the code.

// 在组件选项中使用render函数
export default {
  render() {
    return h('div', 'hello world')
  }
}

// 使用JSX语法创建模板
export default {
  render() {
    return (
      <div>
        <h1 id="Hello-World">Hello World</h1>
      </div>
    )
  }
}

In the render function, we can return different VNode nodes, such as HTML nodes, component nodes, text nodes, etc. At the same time, we can also use control statements such as conditional statements and loop statements to render components according to specific situations.

export default {
  props: {
    msg: String
  },
  render() {
    if (this.msg) {
      return (
        <div>
          <h1 id="this-msg">{this.msg}</h1>
        </div>
      )
    } else {
      return (
        <div>
          <h1 id="No-message">No message</h1>
          <p>Please add message prop</p>
        </div>
      )
    }
  }
}

In the render function, we can also use slots to render flexible components. We can use default slot to define a default slot, or we can define a named slot.

export default {
  render() {
    return (
      <div>
        <h1 id="Header">Header</h1>
        <slot name="content">
          <p>No content provided</p>
        </slot>
        <h1 id="Footer">Footer</h1>
      </div>
    )
  }
}

A named slot is used in this component, and the slot is named content. If no content with name content is provided in the component tag, the default content provided in the slot is used.

Advantages of the render function

render函数提供了比模板更加灵活的自定义渲染方式。
使用render函数可以获得更高性能的组件。
使用render函数可以更好地支持TypeScript和Composition API。
随着Vue3里的Composition API的出现，组件模板要做的事情也逐渐移交给了组件逻辑中的各个功能单元，render函数的运用也就更加广泛。

The render function in Vue3 is one of the exciting new features, which provides a more flexible way to customize rendering. It can be said that mastering the render function is a necessary skill for building excellent Vue3 components. This article has explained to readers in detail what the render function in Vue3 is, how to use it, and its advantages. I hope it can help readers better control the render function and create better Vue3 components.

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