理解Vue 2.0 的ref属性及简单用法

以一个菜单为例：

先搭建一个菜单列表example.vue:

<style src="./example.less" lang="less" scoped></style>
<template>
    <div class="menu">
        <div>
            <div class="side-bar">
            </div>
            <ul class="catalog-list" >
                <li class="level1" v-for="firstLevel in menuList">
                    <em class="circle-pointer"></em>
                    <a href="#" class="title-link">{{firstLevel.name}}</a>
                    <ul v-if="firstLevel.children.length>0">
                        <li class="level2" v-for="secondLevel in firstLevel.children">
                            <em class="pointer"></em>
                            <a href="#" class="title-link">{{secondLevel.name}}</a>

                            <ul v-if="secondLevel.children.length>0">
                                <li class="level3"
                                    @click="moveArrow"
                                    v-for="thirdLevel in secondLevel.children">
                                    <a :href=""#item_"+thirdLevel.id" class="title-link">{{thirdLevel.name}}</a>
                                </li>
                            </ul>
                        </li>
                    </ul>
                </li>
                <li class="last"> <em class="circle-pointer"></em></li>
                <a class="arrow" href="javascript:void(0);"></a>
            </ul>

        </div>

    </div>
</template>
<script src="./example.js"></script>

加载数据menuList后效果如图：

为了让左边箭头随鼠标的点击移动，给三级目录绑定事件

获取当前鼠标点击的top以及外层div元素的top

为了访问到DOM元素的值，要用到ref属性，将以上的最外层Div改写为：

<div class="menu" ref="menuBorder">

就可以将class为menu的dom属性集合，即menuBorder挂载到this.refs上，通过this.refs.menuBorderj就可以访问了

example.js:

export default {
    data() {
        return {
            menuList: [{
                name: "一级目录",
                children: [
                    {
                        name: "二级目录",
                        children: [
                            {
                                name: "三级目录",
                                children: ["内容"]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            }
                        ]
                    },{
                        name: "二级目录",
                        children: [
                            {
                                name: "三级目录",
                                children: ["内容"]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            },
                            {
                                name: "二级目录",
                                children: [{
                                    name: "三级目录",
                                    children: ["内容"]
                                }]
                            }
                        ]
                    }],
            }]
        };
    },

    methods:{
        moveArrow:function (e) {
            console.log($(e.target).offset().top)
            let parentTop=this.$refs.menuBorder.offsetTop;
            var top = $(e.target).offset().top - parentTop;
            $(".arrow").css("top", top );
        }
    }
};

less文件省略……

达到目的，是因为别人让用这个才试着使用，刚开始很模糊，不知道它的目的是什么，然后自己用完一遍后，发现就和选择器差不多效果……………………

自己实践了一下

console.log($(".menu").offset().top);
console.log(this.$refs.menuBorder.offsetTop)

结果：

好吧，一样的………………
只能安慰自己多学习了一点知识
笑 脸