How to use the h function in Vue3

Introduction

• As we all know, what is built inside vue is actually a virtual DOM, and the virtual DOM is generated by a virtual node. In essence, the virtual node is a js object

• In fact, the template we write in vue ultimately generates the corresponding VNode through the rendering function

• And the h function is used to generate VNode Function, its full name is createVNode

Simple use

parameters

It has three parameters in total

The first parameter

• is a string, it is required

• This The string can be an html tag name, a component, an asynchronous component or a function component

The second parameter

• is an object, optional

• Object corresponding to attribute, prop and event

The third one Parameters

• can be a string, an array or an object

• It is VNodes and is created using the h function

Using

<script>
import { h } from &#39;vue&#39;

export default {
    setup() {
        return () => h("h3", null, "Hello World")
    }
}

</script>

The rendering effect is as follows

##Of course we can also use the rener function for rendering

<script>
import { h } from &#39;vue&#39;

export default {
    render() {
        return h("h3", null, "Hello World")
    }
}
</script>

Counter

<script>
import { h } from &#39;vue&#39;

export default {
    data() {
        return {
            counter: 0
        }
    },
    render() {
        return h("div", null, [
            h("h3", null, "计数器"),
            h("h4", null, `计数${this.counter}`),
            h("button", { onClick: () => this.counter++ },"点一下")
        ])
    }
}
</script>

Rendered as follows

Advanced use

Function component

Let’s write a component first

HelloWorld.vue

<script setup lang="ts">
import { ref } from &#39;vue&#39;;

const param = ref("Hello World") 
</script>

<template>
    <h3>{{ param }}</h3>
</template>

<style scoped lang="less"></style>

Then, we introduce this component in the h function, and it will be rendered

<script>
import { h } from &#39;vue&#39;

import HelloWorld from &#39;./HelloWorld.vue&#39;

export default {
    data() {
        return {
            counter: 0
        }
    },
    render() {
        return h("div", null, [h(HelloWorld)])
    }
}
</script>

Slot

h function also supports slots, we change the HelloWorld component into a slot component

HelloWorld.vue

<script setup lang="ts">
import { ref } from &#39;vue&#39;;

const param = ref("Hello World") 
</script>

<template>
    <h3>{{ param }}</h3>
    <slot></slot>
</template>

<style scoped lang="less"></style>

index.ts

<script>
import { h } from &#39;vue&#39;

import HelloWorld from &#39;./HelloWorld.vue&#39;

export default {
    data() {
        return {
            counter: 0
        }
    },
    render() {
        return h("div", null, [h(HelloWorld, {}, [h("div", null, "Hello Slot")])])
    }
}
</script>

The final rendering is as follows

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