vue 判断是否为移动端

import store from '@/store'

const { body } = document
const WIDTH = 992 // refer to Bootstrap's responsive design

mounted() {

      const isMobile = this.$_isMobile()
      if (isMobile) {
          store.dispatch('app/toggleDevice', 'mobile')
          store.dispatch('app/closeSideBar', { withoutAnimation: true })
      }
},

methods: {
    $_isMobile() {
      const rect = body.getBoundingClientRect()
      return rect.width - 1 < WIDTH
},

import Cookies from 'js-cookie'

const state = {

  device: 'desktop',
 
}

const mutations = {

  TOGGLE_DEVICE: (state, device) => {
    state.device = device
  }

}

const actions = {
 
  toggleDevice({ commit }, device) {
    commit('TOGGLE_DEVICE', device)
  },

}

export default {
  namespaced: true,
  state,
  mutations,
  actions
}

<template v-if="device!=='mobile'">
        <search id="header-search" class="right-menu-item" />

    <!--    <el-tooltip content="源码地址" effect="dark" placement="bottom">
          <hejiGit id="heji-git" class="right-menu-item hover-effect" />
        </el-tooltip>

        <el-tooltip content="文档地址" effect="dark" placement="bottom">
          <hejiDoc id="heji-doc" class="right-menu-item hover-effect" />
        </el-tooltip> -->

        <screenfull id="screenfull" class="right-menu-item hover-effect" />

        <el-tooltip content="布局大小" effect="dark" placement="bottom">
          <size-select id="size-select" class="right-menu-item hover-effect" />
        </el-tooltip>

      </template>

computed: {
...mapGetters([
'device'
]),

getBoundingClientRect()判断某个元素是否在可视区域

应用场景

场景：判断某个元素是否出现了可视区域，根据是否在可视区域来执行不同动作；
/**
 * 判断某个原生DOM元素是否不在屏幕可见区内
 * @param {*} el 原生DOM元素
 */

const isElementNotInViewport = function(el) {
  let rect = el.getBoundingClientRect();
  return (
    rect.top >= (window.innerHeight || document.documentElement.clientHeight) ||
    rect.bottom <= 0
  );
};

export { isElementNotInViewport};

isElementNotInViewport在组件内的使用：

import { isElementNotInViewport} from "@/utils/index.js";

  mounted() {
    this.$nextTick(() => {
      let timer;
      window.addEventListener("scroll", () => {
        if (this.isFixed) {
          this.isFixed = false;
        }
        if (timer) {
          clearTimeout(timer);
        }
        timer = setTimeout(() => {
          this.handleScroll();
        }, 200);
      });
      this.handleScroll();
    });
  },
  methods: {
      // 滑动出现底部按钮
    handleScroll() {
      if (isElementNotInViewport(this.$refs.lightBtn)) {
        this.isFixed = true;
      } else {
        this.isFixed = false;
      }
    },
  }

 getBoundingClientRect()用于获得页面中某个元素的左，上，右和下分别相对浏览器视窗的位置。 

getBoundingClientRect()是DOM元素到浏览器可视范围的距离（不包含文档卷起的部分）

该函数返回一个Object对象，该对象有6个属性：top,lef,right,bottom,width,height；