写一个vue的滚动条插件

组件源码如下： vue-scroll.vue

<template>
    <div class="vue-scroll" ref="vueScrollW">
        <div class="vue-scroll-w"  ref="vueScroll" >
            <div class="vue-scroll-c" :style="{cWidth}">
                <slot></slot>
            </div>
        </div>
        <div class="vue-scrollbar" v-if="rate < 1">
            <div class="vue-scrollbar-thumb" 
            :style="{height:thumbH,top:thumbTop}"
            @mousedown="onmousedown"
            @mouseup="onmouseup"
            ></div>
        </div>
    </div>
</template>

<script>



export default {
    name:"vue-scroll",
    data(){
        return {
            thumb:0,
            top:0,
            rate:2,
            moveTop:null,
            isDrag:false,
            cw:10,
            observer:null
        }
    },
    computed:{
        thumbH(){
            return this.thumb + "px";
        },
        thumbTop(){
            return this.top + "px";
        },
        cWidth(){
            return this.cw + "%";
        }
      
    },
    updated(){
        if(!window.MutationObserver){
            this.refresh();
        }
    },
    mounted(){
        var me = this;
        me.$refs.vueScroll.addEventListener("scroll",me.onscroll.bind(me));
        window.addEventListener("mouseup",me.onmouseup.bind(me));
        window.addEventListener("mousemove",me.onmousemove.bind(me));

       if(window.MutationObserver){
           //MutationObserver 最低只兼容 ie11 
            me.observer = new window.MutationObserver(me.mutationCallback.bind(me));
            me.observer.observe(me.$refs.vueScroll, {
                attributes: true,
                childList: true,
                subtree: true
            });
       }
       
        me.refresh();
    },
    methods:{
        mutationCallback(mutationsList){
            this.refresh();
        },
        onscroll(){
            this.top = this.$refs.vueScroll.scrollTop * this.rate; //计算滚动条所在的高度
            if(this.rate < 1){
                this.eventTrigger(this.top);
            }
        },
        refresh(){
            var me = this;
            var vueScroll = me.$refs.vueScroll;
            var rate =  vueScroll.clientHeight / vueScroll.scrollHeight; //滚动条高度的比例,也是滚动条top位置的比例
            me.rate = rate;
            if(rate < 1){
                //需要出现滚动条,并计算滚动条的高度
                me.thumb = rate * vueScroll.clientHeight;  //滚动条的 bar 的高度
                //计算出原生的滚动条的宽度
                var w = me.$refs.vueScrollW.clientWidth;
                //根据比例，转换为内容的百分比
                me.cw =  w/vueScroll.clientWidth *100;
            }else{
                //不需要出现滚动条
                 me.thumb = 0;
                 me.cw = 10;
            }
        },
   
        onmousedown(){
            this.isDrag = true;
            this.moveTop = null;
        },
        onmouseup(){
           this.isDrag = false;
        },
        onmousemove(e){
            if(this.isDrag){
                if(this.moveTop !== null){
                    var speed = e.screenY -  this.moveTop;
                    var top = this.top + speed;
                   this.scrollThumb(top);
                }
                this.moveTop = e.screenY;
                e.preventDefault();
            }
            
        },
        scrollThumb(top){
            if(top < 0 ){
                top = 0;
                
            }
            if(top > this.$refs.vueScroll.clientHeight-this.thumb){
                top = this.$refs.vueScroll.clientHeight-this.thumb;
                
            }
            
            this.$refs.vueScroll.scrollTop = top/this.rate;
            this.top = top;
        },
        eventTrigger(top){
            if(top === 0){
                this.$emit("reachTop"); //到达顶部
            }
            if(top === this.$refs.vueScroll.clientHeight-this.thumb){
                this.$emit("reachBottom"); //到达底部与
            }
            this.$emit("vuescroll",this.$refs.vueScroll.scrollTop,this.top);//返回内容滚动的高度 和  滚动条所在的高度
        },
        scrollTo(scrollTop){
            //对外的api，滚动的内容的哪里
             this.$refs.vueScroll.scrollTop = scrollTop;
             this.$nextTick(()=>{
                 this.onscroll();
             })
        }
    },
    destroyed(){
        var me = this;
        me.$refs.vueScroll && me.$refs.vueScroll.removeEventListener("scroll",me.onscroll.bind(me));
        window.removeEventListener("mouseup",me.onmouseup.bind(me));
        window.removeEventListener("mousemove",me.onmousemove.bind(me));
        me.observer&&me.observer.disconnect();
    }
}
</script>

<style lang="scss" scoped>
.vue-scroll{
    height: 100%;
     100%;
    overflow: hidden;
    position: relative;
    .vue-scroll-w{
         1000%;
        height: 100%;
        overflow: auto;
        .vue-scroll-c{
           position: relative;
            10%;
        }
    }
    .vue-scrollbar{
        position: absolute;
        z-index: 1;
        right: 0;
        top: 0;
         4px;
        height: 100%;
        background: #EEEEEE;
        opacity: 0.6;
        .vue-scrollbar-thumb{
            position: absolute;
            top: 0;
            right: 0;
             4px;
            border-radius: 4px;
            background: #D3D3D3;
            &:hover{
                background: #bbb;
            }
            &:active{
                background: #aaa;
            }
        }
    }
}
</style>

　　

　　

使用：

<template>
    <div class="scroll">
        <vueScroll>
            <ul>
                <li v-for="item in 60" :key="item">{{item}}</li>
            </ul>
        </vueScroll>
    </div>
</template>

<script>
import vueScroll from "@/components/vue-scroll.vue"
export default {
    data(){
        return {
            count:60
        }
    },
    components:{
        vueScroll
    },
    mounted(){
    
    }
}
</script>

<style lang="less" scoped>
.scroll{
     400px;
    height: 600px;
    margin: 0 auto;
    border: 1px solid red;
    ul{
        li{
            line-height: 30px;
            border-bottom: 1px solid #ddd;
        }
    }
}
</style>