Vue render函数实战之实现tabs选项卡组件

用过Element ui库的童鞋肯定知道<el-tabs>组件，简单、好用、可以自定义标签页，不知道广大童鞋们在刚开始使用<el-tabs>组件的时候有没有想过它是如何实现的？我咋刚开始使用<el-tabs>组件的时候就有去想过，也想去实现一个超级简单的tabs选项卡组件，无奈当时功力不够，未能实现。最近的一个简单项目中正好要用到选项卡组件，由于项目简单也就没有使用任何第三方库，于是就自己动手写了个选项卡组件。

1、实现tabs选项卡组件的思考

<el-tabs v-model="activeName" @tab-click="handleClick">
 <el-tab-pane label="用户管理" name="first">用户管理</el-tab-pane>
 <el-tab-pane label="配置管理" name="second">配置管理</el-tab-pane>
 <el-tab-pane label="角色管理" name="third">角色管理</el-tab-pane>
 <el-tab-pane label="定时任务补偿" name="fourth">定时任务补偿</el-tab-pane>
</el-tabs>

问题：

1. 如何根据<el-tab-pane>来生成标签页？
2. 如何过滤<el-tabs>组件中的子元素，使得在使用的时候只显示<el-tab-pane>，而不会显示其他组件或div之类的元素？

2、实现思路

想根据<el-tab-pane>来生成标签页就需要使用到<slot>，使用<slot>用<template>的形式肯定是不行的，因为无法获取到<slot>的数量；使用<template>的形式行不通，那就只有使用render函数了
过滤<el-tabs>组件中的子元素也需要使用render函数

3、代码实现

index.js

import PTabs from './PTabs';
import PTabPane from './PTabPane';

export default function tabsInstall(Vue) {
 if(tabsInstall.installed){
 return;
 }
 Vue.component('PTabs', PTabs);
 Vue.component('PTabPane', PTabPane);
}

PTabs.vue

<script>
 import PTabNav from './PTabNav';
 export default {
 name: "PTabs",
 props: {
  value: {
  type: [String, Number],
  default: ''
  },
  beforeClick: {
  type: Function,
  default(){
   return function () {};
  }
  }
 },
 components: {
  PTabNav
 },
 data(){
  return {
  pTabPanes: [],
  currentName: this.value || 0
  }
 },
 methods: {
  addPane(pane){
  this.pTabPanes.push(pane);
  if(!this.currentName){
   this.setCurrentName(this.pTabPanes[0].name);
  }
  },
  removePane(pane){
  let index = this.pTabPanes.indexOf(pane);
  if(index > -1){
   this.pTabPanes.splice(index, 1);
  }
  },
  setCurrentName(name){
  if(this.currentName !== name){
   this.currentName = name;
   this.$emit('input', name);
  }
  },
  // 标签页点击事件
  handTabNavClick(name, pane, e){
  if(this.currentName === name || pane.disabled){
   return;
  }
  let before = this.beforeClick();
  if(before && before.then){
   before.then(() => {
   this.setCurrentName(name);
   this.$emit('tabClick', pane, e);
   })
  }else{
   this.setCurrentName(name);
   this.$emit('tabClick', pane, e);
  }
  }
 },
 watch: {
  value(newVal){
  this.setCurrentName(newVal);
  },
  currentName(){
  this.$nextTick(() => {
   this.$refs.p_tab_nav.scrollToActiveTab();
  });
  }
 },
 render(h) {
  let {$scopedSlots} = this;
  let $default = $scopedSlots.default();
  let qTabPanes = $default.map(item => {
  /* 过滤<PTabs>xxx</PTabs>中传递的xxx内容。这里只接收<PTabPane>组件，因为我们需要根据<PTabPane>组件的数量来生成
   * <PTabNav>组件，如果参差了其它节点则会导致不能正确生成<PTabNav>组件 */
  if(item.componentOptions && item.componentOptions.tag === 'PTabPane'){
   return item;
  }
  });
  let qTab = h('PTabNav', {
  props: {
   // 将tab-pane传递给 <PTabNav>组件，<PTabNav>组件就知道要有多少个tab-item了
   tabPanes: this.pTabPanes,
   handTabNavClick: this.handTabNavClick
  },
  ref: 'p_tab_nav'
  });
  let qTabBody = h('div', {
  staticClass: 'p-tabs_content'
  }, qTabPanes);

  console.log($default)
  return h('div', {
  staticClass: 'p-tabs'
  }, [qTab, qTabBody]);
 },
 mounted() {
  //console.log(this)
  this.$nextTick(() => {
  this.$refs.p_tab_nav.scrollToActiveTab();
  });
 }
 }
</script>
<style lang="stylus">
.p-tabs{
 .p-tabs_header{
 position: relative;
 margin-bottom: 15px;
 &.is-scrollable{
  padding-left: 20px;
  padding-right: 20px;
 }
 }
 .p-tabs_nav-prev,
 .p-tabs_nav-next{
 position: absolute;
 top: 0;
 width: 20px;
 height: 100%;
 display: none;
 &::before{
  position: absolute;
  content: ' ';
  font-size: 0;
  line-height: 0;
  width: 10px;
  height: 10px;
  top: 50%;
  left: 50%;
  border-top: 1px solid #eee;
  border-left: 1px solid #eee;
  margin: -5px 0 0 -5px;
 }
 cursor: pointer;
 &.disabled{
  cursor: default;
  border-color: #aaa;
 }
 }
 .p-tabs_nav-prev{
 left: 0;
 &:before{
  transform: rotate(-45deg);
 }
 }
 .p-tabs_nav-next{
 right: 0;
 &:before{
  transform: rotate(135deg);
 }
 }
 .p-tabs_header{
 &.is-scrollable{
  .p-tabs_nav-prev,
  .p-tabs_nav-next{
  display: block;
  }
 }
 }
 .p-tabs_nav-scroll{
 overflow: hidden;
 }
 .p-tabs_nav-list{
 position: relative;
 float: left;
 white-space: nowrap;
 transition: transform .3s;
 }
 .p-tabs_nav-item{
 display: inline-block;
 height: 40px;
 line-height: 40px;
 padding: 0 20px;
 color: #fff;
 cursor: pointer;
 &.active,
 &:hover{
  color: #ffb845;
 }
 &.disabled{
  cursor: not-allowed;
  color: #aaa;
  &:hover{
  color: #aaa;
  }
 }
 }
 .p-tabs_content{
 position: relative;
 overflow: hidden;
 }
 .p-tabs-pane{
 color: #fff;
 }
}
</style>

PTabPane.vue

<template>
 <div class="p-tabs-pane" v-show="show">
 <slot></slot>
 </div>
</template>
<script>
 export default {
 name: "PTabPane",
 props: {
  label: {
  type: String,
  default: ''
  },
  name: {
  type: [String, Number],
  default: ''
  },
  disabled: {
  type: Boolean,
  default: false
  }
 },
 data(){
  return {
  loaded: false
  }
 },
 computed: {
  show(){
  if(this.$parent.currentName === this.name){
   if(!this.loaded){
   this.loaded = true;
   }
   return true;
  }
  return false;
  }
 },
 watch: {
  label(){
  // label更新的时候强制更新父组件，以触发PTabNav才能更新
  this.$parent.$forceUpdate();
  }
 },
 mounted() {
  // 当当前组件创建的时候将当前组件添加到父组件的pTabPanes中，以触发PTabNav才能更新
  this.$parent.addPane(this);
 },
 destroyed() {
  if(this.$el && this.$el.parentNode){
  this.$el.parentNode.removeChild(this.$el);
  }
  // 当当前组件销毁时需从父组件中的pTabPanes中移除当前组件，以触发PTabNav才能更新
  this.$parent.removePane(this);
 }
 }
</script>

PTabNav.vue

<script>
 function noop() {};

 export default {
 name: "PTabNav",
 props: {
  tabPanes: {
  type: Array,
  default(){
   return [];
  }
  },
  handTabNavClick: {
  type: Function,
  default(){
   return function () {};
  }
  }
 },
 data(){
  return {
  navPrevDisabled: true,
  navNextDisabled: true,
  // 控制左右箭头显示
  scrollable: false,
  listOffset: 0
  }
 },
 methods: {
  navPrevClickEvent(){
  if(!this.navPrevDisabled){
   let navScrollW = this.$refs.nav_scroll.offsetWidth;
   let navListW = this.$refs.nav_list.offsetWidth;
   let maxTransformX = 0;
   let transformX = this.listOffset - navScrollW;
   if(transformX < maxTransformX){
   transformX = maxTransformX;
   }
   if(transformX === this.listOffset){
   return;
   }
   console.log('上一页按钮点击了', transformX);
   this.listOffset = transformX;
   if(transformX === 0){
   this.navPrevDisabled = true;
   this.navNextDisabled = false;
   }else if(transformX === (navListW - navScrollW)){
   this.navPrevDisabled = false;
   this.navNextDisabled = true;
   }else{
   this.navPrevDisabled = false;
   this.navNextDisabled = false;
   }
  }
  },
  navNextClickEvent(){
  if(!this.navNextDisabled){
   let navScrollW = this.$refs.nav_scroll.offsetWidth;
   let navListW = this.$refs.nav_list.offsetWidth;
   let maxTransformX = navListW - navScrollW;
   let transformX = this.listOffset + navScrollW;
   if(transformX > maxTransformX){
   transformX = maxTransformX;
   }
   if(transformX === this.listOffset){
   return;
   }
   console.log('下一页按钮点击了', transformX);
   this.listOffset = transformX;
   if(transformX === 0){
   this.navPrevDisabled = true;
   this.navNextDisabled = false;
   }else if(transformX === (navListW - navScrollW)){
   this.navPrevDisabled = false;
   this.navNextDisabled = true;
   }else{
   this.navPrevDisabled = false;
   this.navNextDisabled = false;
   }
  }
  },
  // 计算 .p-tabs_nav-list 是否溢出
  calculateListSpilled(){
  let navScrollW = this.$refs.nav_scroll.offsetWidth;
  let navListW = this.$refs.nav_list.offsetWidth;
  if(navScrollW < navListW){
   this.scrollable = true;
  }else{
   if(this.listOffset > 0){
   this.listOffset = 0;
   }
   this.scrollable = false;
  }
  },
  // 滚动条滚动到激活的tab
  scrollToActiveTab(){
  if(this.scrollable){
   this.$nextTick(() => {
   let navScrollW = this.$refs.nav_scroll.offsetWidth;
   let navList = this.$refs.nav_list;
   let activeTab = navList.querySelector('.active');
   let activeTabOffsetLeft = 0;
   if(activeTab){
    activeTabOffsetLeft = activeTab.offsetLeft;
   }

   let transformX = activeTabOffsetLeft + activeTab.offsetWidth - navScrollW;

   transformX = transformX < 0 ? 0 : transformX;
   this.listOffset = transformX;
   if(transformX === 0){
    this.navPrevDisabled = true;
    this.navNextDisabled = false;
   }else if(transformX === (navList.offsetWidth - navScrollW)){
    this.navPrevDisabled = false;
    this.navNextDisabled = true;
   }else{
    this.navPrevDisabled = false;
    this.navNextDisabled = false;
   }
   });
  }
  }
 },
 computed: {
  listOffsetTran(){
  console.log('dddd',`translateX(-${this.listOffset}px);`)
  return {
   transform: `translateX(-${this.listOffset}px)`
  }
  }
 },
 render(h) {
 /*dom结构
 <div class="p-tabs_header is-scrollable">
  <span class="p-tabs_nav-prev disabled"></span>
  <span class="p-tabs_nav-next"></span>
  <div class="p-tabs_nav-scroll">
  <div class="p-tabs_nav-list">
   <div class="p-tabs_nav-item active">全部</div>
   <div class="p-tabs_nav-item disabled">技术教学</div>
   <div class="p-tabs_nav-item">新手教学</div>
  </div>
  </div>
 </div>
 */
  let navPrev = h('span', {
  staticClass: 'p-tabs_nav-prev',
  'class': {
   disabled: this.navPrevDisabled
  },
  on: {
   click: this.navPrevClickEvent
  }
  });
  let navNext = h('span', {
  staticClass: 'p-tabs_nav-next',
  'class': {
   disabled: this.navNextDisabled
  },
  on: {
   click: this.navNextClickEvent
  }
  });
  // 生成标签页
  let navItems = this.tabPanes.map(item => {
  let $labelSlot = item.$scopedSlots.label ? item.$scopedSlots.label() : null;
  let labelContent = $labelSlot ? $labelSlot : item.label;
  return h('div', {
   staticClass: 'p-tabs_nav-item',
   'class': {
   active: this.$parent.currentName === item.name,
   disabled: item.disabled,
   },
   on: {
   click: (e) => {
    this.handTabNavClick(item.name, item, e);
   }
   }
  }, [labelContent]);
  });
  let navScroll = h('div', {
  staticClass: 'p-tabs_nav-scroll',
  ref: 'nav_scroll'
  }, [
  h('div', {
   staticClass: 'p-tabs_nav-list',
   ref: 'nav_list',
   style: this.listOffsetTran
  }, [navItems])
  ]);

  return h('div', {
  staticClass: 'p-tabs_header',
  'class': {
   'is-scrollable': this.scrollable
  },
  }, [navPrev, navNext, navScroll]);
 },
 updated(){
  this.calculateListSpilled();
 },
 mounted() {
  this.calculateListSpilled();
 }
 }
</script>

4、使用

main.js

// 引入tabs组件
import tabs from './components/p-tabs';
// 全局注册p-tabs组件
Vue.use(tabs);

页面中使用

<PTabs v-model="activeName">
 <PTabPane label="用户管理" name="first">用户管理</PTabPane>
 <PTabPane label="配置管理" name="second">配置管理</PTabPane>
 <PTabPane label="角色管理" name="third">角色管理</PTabPane>
 <PTabPane label="定时任务补偿" name="fourth">定时任务补偿</PTabPane>
</PTabs>

总结

以上所述是小编给大家介绍的Vue render函数实战之实现tabs选项卡组件,希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对我们网站的支持！
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