.sidebar {
 position: fixed;
 border-right: 1px solid rgba(0,0,0,.07);
 overflow-y: auto;
 position: absolute;
 top: 0;
 bottom: 0;
 left: 0;
 transition: transform .25s ease-out;
 width: 300px;
 z-index: 3;
}
.sidebar::-webkit-scrollbar {
 width: 4px
}

.sidebar::-webkit-scrollbar-thumb {
 background: transparent;
 border-radius: 4px
}

.sidebar:hover::-webkit-scrollbar-thumb {
 background: hsla(0,0%,53%,.4)
}

.sidebar:hover::-webkit-scrollbar-track {
 background: hsla(0,0%,53%,.1)
}

props: {
 native: Boolean, // 是否使用本地，設為true則不會啟用element-ui自定義的滾動條
 wrapStyle: {}, // 包裹層自定義樣式
 wrapClass: {}, // 包裹層自定義樣式類
 viewClass: {}, // 可滾動部分自定義樣式類
 viewStyle: {}, // 可滾動部分自定義樣式
 noresize: Boolean, // 如果 container 尺寸不會發生變化，最好設置它可以優化性能
 tag: { // 生成的標簽類型，默認使用 `div`標簽包裹
 type: String,
 default: 'div'
 }
}

<template>
 <div>
 <el-scrollbar :native="false" wrapStyle="" wrapClass="" viewClass="" viewStyle="" noresize="false" tag="section">
 <div>
 <p v-for="(item, index) in 200" :key="index">{{index}} 這里是一些文本。</p>
 </div>
 <el-scrollbar>
 </div>
</template>

import Scrollbar from './src/main';

/* istanbul ignore next */
Scrollbar.install = function(Vue) {
 Vue.component(Scrollbar.name, Scrollbar);
};

export default Scrollbar;

// reference https://github.com/noeldelgado/gemini-scrollbar/blob/master/index.js

import { addResizeListener, removeResizeListener } from 'element-ui/src/utils/resize-event';
import scrollbarWidth from 'element-ui/src/utils/scrollbar-width';
import { toObject } from 'element-ui/src/utils/util';
import Bar from './bar';

/* istanbul ignore next */
export default {
 name: 'ElScrollbar',

 components: { Bar },

 props: {
 native: Boolean,
 wrapStyle: {},
 wrapClass: {},
 viewClass: {},
 viewStyle: {},
 noresize: Boolean, // 如果 container 尺寸不會發生變化，最好設置它可以優化性能
 tag: {
 type: String,
 default: 'div'
 }
 },

 data() {
 return {
 sizeWidth: '0',
 sizeHeight: '0',
 moveX: 0,
 moveY: 0
 };
 },

 computed: {
 wrap() {
 return this.$refs.wrap;
 }
 },

 render(h) {
 let gutter = scrollbarWidth();
 let style = this.wrapStyle;

 if (gutter) {
 const gutterWith = `-${gutter}px`;
 const gutterStyle = `margin-bottom: ${gutterWith}; margin-right: ${gutterWith};`;

 if (Array.isArray(this.wrapStyle)) {
 style = toObject(this.wrapStyle);
 style.marginRight = style.marginBottom = gutterWith;
 } else if (typeof this.wrapStyle === 'string') {
 style += gutterStyle;
 } else {
 style = gutterStyle;
 }
 }
 const view = h(this.tag, {
 class: ['el-scrollbar__view', this.viewClass],
 style: this.viewStyle,
 ref: 'resize'
 }, this.$slots.default);
 const wrap = (
 <div
 ref="wrap"
 style={ style }
 onScroll={ this.handleScroll }
 class={ [this.wrapClass, 'el-scrollbar__wrap', gutter ? '' : 'el-scrollbar__wrap--hidden-default'] }>
 { [view] }
 </div>
 );
 let nodes;

 if (!this.native) {
 nodes = ([
 wrap,
 <Bar
 move={ this.moveX }
 size={ this.sizeWidth }></Bar>,
 <Bar
 vertical
 move={ this.moveY }
 size={ this.sizeHeight }></Bar>
 ]);
 } else {
 nodes = ([
 <div
 ref="wrap"
 class={ [this.wrapClass, 'el-scrollbar__wrap'] }
 style={ style }>
 { [view] }
 </div>
 ]);
 }
 return h('div', { class: 'el-scrollbar' }, nodes);
 },

 methods: {
 handleScroll() {
 const wrap = this.wrap;

 this.moveY = ((wrap.scrollTop * 100) / wrap.clientHeight);
 this.moveX = ((wrap.scrollLeft * 100) / wrap.clientWidth);
 },

 update() {
 let heightPercentage, widthPercentage;
 const wrap = this.wrap;
 if (!wrap) return;

 heightPercentage = (wrap.clientHeight * 100 / wrap.scrollHeight);
 widthPercentage = (wrap.clientWidth * 100 / wrap.scrollWidth);

 this.sizeHeight = (heightPercentage < 100) ? (heightPercentage + '%') : '';
 this.sizeWidth = (widthPercentage < 100) ? (widthPercentage + '%') : '';
 }
 },

 mounted() {
 if (this.native) return;
 this.$nextTick(this.update);
 !this.noresize && addResizeListener(this.$refs.resize, this.update);
 },

 beforeDestroy() {
 if (this.native) return;
 !this.noresize && removeResizeListener(this.$refs.resize, this.update);
 }
};

<div style="height: 100vh;">
 <!-- 注意需要給 el-scrollbar 設置高度，判斷是否滾動是看它的height判斷的 -->
 <el-scrollbar style="height: 100%;"> <!-- 滾動條 -->
 <div style="height: 500px;width: 100%;background: red;"></div>
 <div style="height: 500px;width: 100%;background: yellowgreen;"></div>
 <div style="height: 500px;width: 100%;background: blueviolet;"></div>
 </el-scrollbar><!-- /滾動條 -->
</div>