在学习Vue.js时，使用vue-cli创建了一个Vue项目，main.js文件中有一行经典代码 render: h => h(App)，那她是什么意思呢？
main.js 文件内容
import Vue from 'vue'
import App from './App.vue'
new Vue({
el: '#app',
render: h => h(App)
})
接下来就是答案喽
{
render: h => h(App);
}
等价于
{
render: h => {
return h(App);
}
}
等价于
{
render: function(h) {
return h(App);
}
}
即：
{
render: function(createElement) {
return createElement(App);
}
}
上一个示例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<div id="app"></div>
<script type="text/javascript" src="https://unpkg.com/vue"></script>
<script type="text/javascript">
var app = new Vue({
el: '#app', // 提供一个在页面上已经存在的 DOM 元素作为 Vue 实例挂载目标
render: function (createElement) {
return createElement('h2', 'Hello Vue!');
}
});
</script>
</body>
</html>
createElement 有这么几个重要的参数
第一个参数(必须) - {String | Object | Function}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<elem></elem>
</div>
<script>
Vue.component('elem', {
render: function(createElement) {
return createElement('div');//一个HTML标签字符
/*return createElement({
template: '<div></div>'//组件选项对象
});*/
/*var func = function() {
return {template: '<div></div>'}
};
return createElement(func());//一个返回HTML标签字符或组件选项对象的函数*/
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
第二个参数(可选) - {Object}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<elem></elem>
</div>
<script>
Vue.component('elem', {
render: function(createElement) {
var self = this;
return createElement('div', {//一个包含模板相关属性的数据对象
'class': {
foo: true,
bar: false
},
style: {
color: 'red',
fontSize: '14px'
},
attrs: {
id: 'foo'
},
domProps: {
innerHTML: 'baz'
}
});
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
第三个参数(可选) - {String | Array}
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<elem></elem>
</div>
<script>
Vue.component('elem', {
render: function(createElement) {
var self = this;
// return createElement('div', '文本');//使用字符串生成文本节点
return createElement('div', [//由createElement函数构建而成的数组
createElement('h1', '主标'),//createElement函数返回VNode对象
createElement('h2', '副标')
]);
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
两种组件写法对比
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<ele></ele>
</div>
<script>
/*Vue.component('ele', {
template: '<div id="elem" :class="{show: show}" @click="handleClick">文本</div>',
data: function() {
return {
show: true
}
},
methods: {
handleClick: function() {
console.log('clicked!');
}
}
});*/
Vue.component('ele', {
render: function(createElement) {
return createElement('div', {
'class': {
show: this.show
},
attrs: {
id: 'elem'
},
on: {
click: this.handleClick
}
}, '文本');
},
data: function() {
return {
show: true
}
},
methods: {
handleClick: function() {
console.log('clicked!');
}
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
this.$slots用法
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<blog-post>
<h1 slot="header"><span>About Me</span></h1>
<p>Here's some page content</p>
<p slot="footer">Copyright 2016 Evan You</p>
<p>If I have some content down here</p>
</blog-post>
</div>
<script>
Vue.component('blog-post', {
render: function(createElement) {
var header = this.$slots.header,//返回由VNode组成的数组
body = this.$slots.default,
footer = this.$slots.footer;
return createElement('div', [
createElement('header', header),
createElement('main', body),
createElement('footer', footer)
])
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
使用props传递数据
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<ele :show="show"></ele>
<ele :show="!show"></ele>
</div>
<script>
Vue.component('ele', {
render: function(createElement) {
if (this.show) {
return createElement('p', 'true');
} else {
return createElement('p', 'false');
}
},
props: {
show: {
type: Boolean,
default: false
}
}
});
new Vue({
el: '#app',
data: {
show: false
}
});
</script>
</body>
</html>
VNodes必须唯一
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<!-- VNode必须唯一 -->
<div id="app">
<ele></ele>
</div>
<script>
var child = {
render: function(createElement) {
return createElement('p', 'text');
}
};
/*Vue.component('ele', {
render: function(createElement) {
var childNode = createElement(child);
return createElement('div', [
childNode, childNode//VNodes必须唯一，渲染失败
]);
}
});*/
Vue.component('ele', {
render: function(createElement) {
return createElement('div',
Array.apply(null, {
length: 2
}).map(function() {
return createElement(child)//正确写法
})
);
}
});
new Vue({
el: '#app'
})
</script>
</body>
</html>
v-model指令
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<el-input :name="name" @input="val=>name=val"></el-input>
<div>你的名字是{{name}}</div>
</div>
<script>
Vue.component('el-input', {
render: function(createElement) {
var self = this;
return createElement('input', {
domProps: {
value: self.name
},
on: {
input: function(event) {
self.$emit('input', event.target.value);
}
}
})
},
props: {
name: String
}
});
new Vue({
el: '#app',
data: {
name: 'hdl'
}
});
</script>
</body>
</html>
作用域插槽
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<ele>
<template scope="props">
<span>{{props.text}}</span>
</template>
</ele>
</div>
<script>
Vue.component('ele', {
render: function(createElement) {
// 相当于<div><slot :text="msg"></slot></div>
return createElement('div', [
this.$scopedSlots.default({
text: this.msg
})
]);
},
data: function() {
return {
msg: '来自子组件'
}
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
向子组件中传递作用域插槽
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<ele></ele>
</div>
<script>
Vue.component('ele', {
render: function(createElement) {
return createElement('div', [
createElement('child', {
scopedSlots: {
default: function(props) {
return [
createElement('span', '来自父组件'),
createElement('span', props.text)
];
}
}
})
]);
}
});
Vue.component('child', {
render: function(createElement) {
return createElement('b', this.$scopedSlots.default({text: '我是组件'}));
}
});
new Vue({
el: '#app'
});
</script>
</body>
</html>
函数化组件
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>render</title>
<script src="https://cdn.bootcss.com/vue/2.3.4/vue.js"></script>
</head>
<body>
<div id="app">
<smart-item :data="data"></smart-item>
<button @click="change('img')">切换为图片为组件</button>
<button @click="change('video')">切换为视频为组件</button>
<button @click="change('text')">切换为文本组件</button>
</div>
<script>
// 图片组件选项
var ImgItem = {
props: ['data'],
render: function(createElement) {
return createElement('div', [
createElement('p', '图片组件'),
createElement('img', {
attrs: {
src: this.data.url
}
})
]);
}
}
// 视频组件
var VideoItem = {
props: ['data'],
render: function(createElement) {
return createElement('div', [
createElement('p', '视频组件'),
createElement('video', {
attrs: {
src: this.data.url,
controls: 'controls',
autoplay: 'autoplay'
}
})
]);
}
};
/*纯文本组件*/
var TextItem = {
props: ['data'],
render: function(createElement) {
return createElement('div', [
createElement('p', '纯文本组件'),
createElement('p', this.data.text)
]);
}
};
Vue.component('smart-item', {
functional: true,
render: function(createElement, context) {
function getComponent() {
var data = context.props.data;
if (data.type === 'img') return ImgItem;
if (data.type === 'video') return VideoItem;
return TextItem;
}
return createElement(
getComponent(),
{
props: {
data: context.props.data
}
},
context.children
)
},
props: {
data: {
type: Object,
required: true
}
}
});
new Vue({
el: '#app',
data() {
return {
data: {}
}
},
methods: {
change: function(type) {
if (type === 'img') {
this.data = {
type: 'img',
url: 'https://raw.githubusercontent.com/iview/iview/master/assets/logo.png'
}
} else if (type === 'video') {
this.data = {
type: 'video',
url: 'http://vjs.zencdn.net/v/oceans.mp4'
}
} else if (type === 'text') {
this.data = {
type: 'text',
content: '这是一段纯文本'
}
}
}
},
created: function() {
this.change('img');
}
});
</script>
</body>
</html>
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