``javascript，class ScrollBar {， constructor(container) {， this.container = container;， this.init();， }，， init() {， const scrollbar = document.createElement('div');， scrollbar.style.width = '10px';， scrollbar.style.background = '#ddd';， scrollbar.style.position = 'absolute';， scrollbar.style.right = '0';， scrollbar.style.top = '0';， scrollbar.style.bottom = '0';， this.scrollbar = scrollbar;， this.container.appendChild(this.scrollbar);，， this.handle = document.createElement('div');， this.handle.style.width = '50px';， this.handle.style.background = '#888';， this.handle.style.position = 'absolute';， this.handle.style.cursor = 'grab';， this.handle.style.userSelect = 'none';， this.handle.style.height = '20px';， this.handle.style.borderRadius = '10px';， this.handle.style.marginTop = '-10px';， this.handle.addEventListener('mousedown', this.startDrag.bind(this));， this.scrollbar.appendChild(this.handle);，， this.container.addEventListener('scroll', () => {， const maxScrollTop = this.container.scrollHeight this.container.clientHeight;， const scrollRatio = this.container.scrollTop / maxScrollTop;， this.handle.style.top = ${scrollRatio * (this.container.clientHeight this.handle.offsetHeight)}px;， });，， this.updateHandleSize();， }，， startDrag(event) {， event.preventDefault();， const startY = event.clientY;， const startTop = parseInt(this.handle.style.top, 10);， const containerRect = this.container.getBoundingClientRect();， const maxScrollTop = this.container.scrollHeight this.container.clientHeight;， const handleHeight = this.handle.offsetHeight;，， const onMouseMove = (moveEvent) => {， const deltaY = moveEvent.clientY startY;， const newTop = Math.min(Math.max(startTop + deltaY, 0), containerRect.height handleHeight);， const scrollRatio = newTop / (containerRect.height handleHeight);， this.container.scrollTop = scrollRatio * maxScrollTop;， };，， const onMouseUp = () => {， document.removeEventListener('mousemove', onMouseMove);， document.removeEventListener('mouseup', onMouseUp);， };，， document.addEventListener('mousemove', onMouseMove);， document.addEventListener('mouseup', onMouseUp);， }，， updateHandleSize() {， const containerHeight = this.container.clientHeight;， const contentHeight = this.container.scrollHeight;， const handleHeight = Math.max((contentHeight / containerHeight) * containerHeight, 30); // Minimum handle height of 30px， this.handle.style.height = ${handleHeight}px;， }，}，，// 使用示例，const myContainer = document.getElementById('myContainer');，new ScrollBar(myContainer);，``