原生js实现自定义滚动条组件

本文实例为大家分享了js实现自定义滚动条组件的具体代码，供大家参考，具体内容如下

功能需求：

1、按照数据结构创建菜单内容，显示在页面中；
2、点击菜单后，显示对应的下级菜单内容，如果整体内容溢出，则出现滚动条；
3、滚动条的高度要随着整体内容高度的改变而改变。
4、鼠标拖动滚动条，整体内容要随着向上滚动。
5、当鼠标滚动时，滚动条和整体内容也要相应滚动。

来看一下效果：

默认状态：

点击菜单，内容溢出后，出现滚动条；

鼠标拖动滚动条，整体内容随着向上滚动：

分析：

• 这个案例中包括折叠菜单和滚动条两个组件 ，所以可以分开来写，然后整合到一起。
• 折叠菜单中要考虑多级菜单出现的情况，使用递归来做，数据的结构一定要统一，方便对数据进行处理。
• 滚动条的创建中，有两个比例等式，一是滚动条的高度/外层div高度=外层div高度/整体内容高度；二是滚动条的位置/（外层div高度-滚动条高度）=内容的scrollTop/（整体内容的高度-外层div高度）
• 当点击折叠菜单后，需要相应地设置滚动条的高度。折叠菜单是在Menu.js文件中，滚动条的设置是在ScrollBar.js文件中，需要进行抛发、监听事件。
• 监听菜单鼠标滚动的事件，当鼠标滚动时，判断滚轮方向，设置滚动条和内容的 top 值，也需要用到事件的抛发和监听。

下面附上代码：

html结构，模拟数据，创建外层容器：

<!DOCTYPE html>
<html lang="en">
<head>
 <meta charset="UTF-8">
 <meta name="viewport" content="width=device-width, initial-scale=1.0">
 <title>scrollBar</title>
</head>
<body>
 <script type="module">
 import Utils from './js/Utils.js';
 import Menu from './js/Menu.js';
 import ScrollBar from './js/ScrollBar.js';
 var arr=[
  {name:"A",category:[
  {name:"奥迪",category:[
   {name:"奥迪A3",href:""},
   {name:"奥迪A4L",category:[
   {name:"奥迪A4L-1",href:""}
   ]},
   {name:"奥迪Q3",href:""},
   {name:"奥迪Q5L",href:""},
   {name:"奥迪Q2L",href:""},
   {name:"奥迪Q7(进口)",href:""},
   {name:"奥迪Q8（进口）",href:""},
   {name:"奥迪Q7新能源",href:""},
  ]},
  {name:"阿尔法-罗密欧",category:[
   {name:"Stelvio（进口）",href:""},
   {name:"Giulia（进口）",href:""},
  ]}
  ]},
  {name:"B",category:[
  {name:"奔驰",category:[
   {name:"奔驰C级",href:""},
   {name:"奔驰E级",href:""},
   {name:"奔驰GLA级",href:""},
   {name:"奔驰GLC级",href:""},
   {name:"奔驰A级",href:""},
   {name:"奔驰E级(进口)",href:""},
   {name:"奔驰A级（进口）",href:""},
   {name:"奔驰B级（进口）",href:""},
   {name:"威霆",href:""},
   {name:"奔驰V级",href:""},
  ]},
  {name:"宝马",category:[
   {name:"宝马5系",href:""},
   {name:"宝马1系",href:""},
   {name:"宝马X1",href:""},
   {name:"宝马X5（进口）",href:""},
   {name:"宝马X6（进口）",href:""},
  ]},
  {name:"本田",category:[
   {name:"竞瑞",href:""},
   {name:"思域",href:""},
   {name:"本田CR-V",href:""},
   {name:"本田XR-V",href:""},
   {name:"本田UR-V",href:""},
   {name:"艾力绅",href:""},
   {name:"享域",href:""},
   {name:"INSPIRE",href:""},
   {name:"凌派",href:""},
   {name:"雅阁",href:""},
   {name:"缤智",href:""},
  ]},
  {name:"别克",category:[
   {name:"凯越",href:""},
   {name:"英朗",href:""},
   {name:"威朗",href:""},
   {name:"阅朗",href:""},
   {name:"君威",href:""},
   {name:"君越",href:""},
   {name:"昂科拉",href:""},
   {name:"昂科威",href:""},
   {name:"别克GL8",href:""},
   {name:"别克GL6",href:""},
   {name:"VELITE",href:""},
  ]}
  ]}
 ]
 var container;
 init();
 function init(){
  createMenu(arr);
  createScrollBar();
 }
  function createMenu(arr){
  //创建菜单
  let menu=new Menu(arr);
  //创建最外层容器
  container=Utils.createE("div",{
  width:"235px",
  height:"360px",
  border:"1px solid #ccc",
  position:"relative",
  overflow:"hidden"
  })
  menu.appendTo(container);
  Utils.appendTo(container,"body")
 }
 function createScrollBar(){
  //创建滚动条
  let scrollBar=new ScrollBar(container);
  scrollBar.appendTo(container);
 }
 </script>
</body>
</html>

Menu.js文件，根据数据创建折叠菜单内容：

import Utils from './Utils.js';
export default class Menu{
 static SET_BAR_HEIGHT="set_bar_height";
 static MOUSE_WHEEL_EVENT="mouse_wheel_event";
 constructor(_list){
 this.elem=this.createElem(_list);
 }
 createElem(_list){
 if(this.elem) return this.elem;
 //创建最外层ul容器
 let ul=Utils.createE("ul",{
  listStyle:"none",
  padding:"0px",
  margin:"0px",
  width:"235px",
  height:"360px",
  color:"#333",
  fontSize:"14px",
  userSelect: "none",
  position:"absolute"
 });
 //创建li列表
 this.createMenu(_list,ul);
 //ul监听点击事件
 ul.addEventListener("click",e=>this.clickHandler(e));
 //ul监听滚轮事件，火狐使用DOMMouseScroll，其它浏览器使用mousewheel
 ul.addEventListener("mousewheel",e=>this.mouseWheelHandler(e));
 ul.addEventListener("DOMMouseScroll",e=>this.mouseWheelHandler(e));
 return ul;
 }
 appendTo(parent){
 Utils.appendTo(this.elem,parent);
 }
 //创建一级菜单
 createMenu(_list,parent){
 for(let i=0;i<_list.length;i++){
  let li=Utils.createE("li",{
  background:"#f5f5f5",
  borderTop:"1px solid #ddd",
  lineHeight:"32px",
  },{
  data:1,//控制一级菜单不能点击折叠
  })
  let span=Utils.createE("span",{
  marginLeft:"14px",
  fontSize:"18px"
  },{
  textContent:_list[i].name
  })
  Utils.appendTo(span,li);
  Utils.appendTo(li,parent);
  //创建子菜单,第三个参数控制子菜单是否显示
  this.createSubMenu(_list[i].category,li,0);
 }
 }
 //创建子菜单
 createSubMenu(_subList,_parent,_index){
 //如果没有子菜单，则跳出
 if(_subList.length===0) return;
 let subUl=Utils.createE("ul",{
  listStyle:"none",
  background:"#fff",
  padding:"0px",
  margin:"0px",
  fontSize:"14px",
  display:_index===0? "block" : "none"
 })
 for(let i=0;i<_subList.length;i++){
  let subLi=Utils.createE("li",{
  paddingLeft:"40px",
  position:"relative",
  cursor:"pointer"
  })
  if(!_subList[i].category){
  //如果当前菜单没有子菜单，则创建a标签，进行跳转
  let subA=Utils.createE("a",{
   color:"#333",
   textDecoration:"none",
   width:"100%",
   display:"inline-block"
  },{
   textContent:_subList[i].name,
   href:_subList[i].href || "javascript:void(0)",
   target:_subList[i].href ? "_blank" : "_self"
  })
  Utils.appendTo(subA,subLi);
  }else{
  //如果当前菜单有子菜单，创建span标签
  let subSpan=Utils.createE("span",{
   position:"absolute",
   left:"20px",
   top:"8px",
   border: "1px solid #ccc",
   display: "inline-block",
   width: "10px",
   height: "10px",
   lineHeight:"8px"
  },{
   textContent:_subList[i].category.length>0? "+" : "-"
  })
  subLi.textContent=_subList[i].name;
  Utils.appendTo(subSpan,subLi);
  }
  Utils.appendTo(subLi,subUl);
  //如果当前菜单没有子菜单，则跳过下面的执行
  if(!_subList[i].category) continue;
  //将当前菜单的子菜单作为参数，进行递归
  this.createSubMenu(_subList[i].category,subLi,1);
 }
 Utils.appendTo(subUl,_parent);
 }
 clickHandler(e){
 //如果当前点击的不是li标签或者span，直接跳出
 if(e.target.nodeName!=="LI" && e.target.nodeName!=="SPAN") return;
 let targ;
 if(e.target.nodeName==="SPAN") targ=e.target.parentElement;
 else targ=e.target;
 //如果当前点击Li下面没有子菜单，直接跳出
 if(targ.children.length<=1) return;
 //如果当前点击的是一级菜单，直接跳出
 if(targ.data===1) return;
 //控制当前点击的Li下的ul显示隐藏
 if(!targ.bool) targ.lastElementChild.style.display="block";
 else targ.lastElementChild.style.display="none";
 targ.bool=!targ.bool;
 //改变span标签的内容
 this.changeSpan(targ);
 //抛发事件,改变滚动条的高度
 var evt=new Event(Menu.SET_BAR_HEIGHT);
 document.dispatchEvent(evt)
 }
 changeSpan(elem){
 if(elem.lastElementChild.style.display==="block"){
  elem.firstElementChild.textContent="-";
 }else{
  elem.firstElementChild.textContent="+";
 }
 }
 mouseWheelHandler(e){
 //阻止事件冒泡
 e.stopPropagation();
 //火狐浏览器判断e.detail，e.detail<0时,表示滚轮往下，页面往上
 let tag=e.detail,wheelDir;
 //其他浏览器判断e.deltaY，e.deltaY<0时，表示滚轮往下，页面往上
 if(tag===0) tag=e.deltaY;

 if(tag>0){
  //滚轮往下滚动，页面往上走
  wheelDir="down";
 }else{
  wheelDir="up";
 }
 //抛发事件，将滚轮方向传递过去
 let evt=new Event(Menu.MOUSE_WHEEL_EVENT);
 evt.wheelDirection=wheelDir;
 this.elem.dispatchEvent(evt);
 }
}

ScrollBar.js文件，创建滚动条，对滚动条进行操作：

import Utils from './Utils.js';
import Menu from './Menu.js';
export default class ScrollBar {
 bar;
 conHeight;
 menuHeight;
 wheelSpeed=6;
 barTop=0;
 static SET_BAR_HEIGHT="set_bar_height";
 constructor(parent) {
 this.container = parent;
 this.menuUl=this.container.firstElementChild;
 this.elem = this.createElem();
 //侦听菜单的点击事件，动态改变滚动条的高度
 document.addEventListener(ScrollBar.SET_BAR_HEIGHT,()=>this.setBarHeight());
 //ul菜单侦听滚轮事件
 this.menuUl.addEventListener(Menu.MOUSE_WHEEL_EVENT,e=>this.mouseWheelHandler(e));
 }
 createElem() {
 if (this.elem) return this.elem;
 //创建滚动条的外层容器
 let div = Utils.createE("div", {
  width: "8px",
  height: "100%",
  position: "absolute",
  right: "0px",
  top: "0px",
 })
 this.createBar(div);
 return div;
 }
 appendTo(parent) {
 Utils.appendTo(this.elem,parent);
 }
 createBar(_parent) {
 if(this.bar) return this.bar;
 //创建滚动条
 this.bar = Utils.createE("div", {
  width: "100%",
  position: "absolute",
  left: "0px",
  top: "0px",
  borderRadius: "10px",
  backgroundColor: "rgba(255,0,0,.5)"
 })
 //设置滚动条hover状态的样式
 this.bar.addEventListener("mouseenter",e=>this.setMouseStateHandler(e));
 this.bar.addEventListener("mouseleave",e=>this.setMouseStateHandler(e));
 //设置滚动条的高度
 this.setBarHeight();
 //侦听鼠标拖动事件
 this.mouseHand = e => this.mouseHandler(e);
 this.bar.addEventListener("mousedown", this.mouseHand);
 Utils.appendTo(this.bar, _parent);
 }
 setBarHeight() {
 //外层父容器的高度
 this.conHeight = this.container.clientHeight;
 //实际内容的高度
 this.menuHeight = this.container.firstElementChild.scrollHeight;
 //如果实际内容的高度小于父容器的高度，滚动条隐藏
 if (this.conHeight >= this.menuHeight) this.bar.style.display = "none";
 else this.bar.style.display = "block";
 //计算滚动条的高度
 let h = Math.floor(this.conHeight / this.menuHeight * this.conHeight);
 this.bar.style.height = h + "px";
 }
 setMouseStateHandler(e){
 //设置滚动条hover状态的样式
 if(e.type==="mouseenter"){
  this.bar.style.backgroundColor="rgba(255,0,0,1)";
 }else{
  this.bar.style.backgroundColor="rgba(255,0,0,.5)";
 }
 }
 mouseHandler(e) {
 switch (e.type) {
  case "mousedown":
  e.preventDefault();
  this.y = e.offsetY;
  document.addEventListener("mousemove", this.mouseHand);
  document.addEventListener("mouseup", this.mouseHand);
  break;
  case "mousemove":
  //注意：getBoundingClientRect()返回的结果中，width height 都是包含border的
  var rect = this.container.getBoundingClientRect();
  this.barTop = e.clientY - rect.y - this.y;
  //滚动条移动
  this.barMove();
  break;
  case "mouseup":
  document.removeEventListener("mousemove", this.mouseHand);
  document.removeEventListener("mouseup", this.mouseHand);
  break;
 }
 }
 mouseWheelHandler(e){
 //滚轮事件
 if(e.wheelDirection==="down"){
  //滚动往下，菜单内容往上
  this.barTop+=this.wheelSpeed;
 }else{
  this.barTop-=this.wheelSpeed;
 }
 //滚动条移动
 this.barMove();
 }
 barMove(){
 if (this.barTop < 0) this.barTop = 0;
 if (this.barTop > this.conHeight - this.bar.offsetHeight) this.barTop = this.conHeight - this.bar.offsetHeight;
 this.bar.style.top = this.barTop + "px";
 //菜单内容滚动
 this.menuMove();
 }
 menuMove(){
 //计算内容的滚动高度
 let menuTop=this.barTop/(this.conHeight-this.bar.offsetHeight)*(this.menuHeight-this.conHeight);
 this.menuUl.style.top=-menuTop+"px";
 }
}

Utils.js文件，是一个工具包：

export default class Utils{
 static createE(elem,style,prep){
 elem=document.createElement(elem);
 if(style) for(let prop in style) elem.style[prop]=style[prop];
 if(prep) for(let prop in prep) elem[prop]=prep[prop];
 return elem;
 }
 static appendTo(elem,parent){
 if (parent.constructor === String) parent = document.querySelector(parent);
 parent.appendChild(elem);
 }
 static randomNum(min,max){
 return Math.floor(Math.random*(max-min)+min);
 }
 static randomColor(alpha){
 alpha=alpha||Math.random().toFixed(1);
 if(isNaN(alpha)) alpha=1;
 if(alpha>1) alpha=1;
 if(alpha<0) alpha=0;
 let col="rgba(";
 for(let i=0;i<3;i++){
  col+=Utils.randomNum(0,256)+",";
 }
 col+=alpha+")";
 return col;
 }
 static insertCss(select,styles){
 if(document.styleSheets.length===0){
  let styleS=Utils.createE("style");
  Utils.appendTo(styleS,document.head);
 }
 let styleSheet=document.styleSheets[document.styleSheets.length-1];
 let str=select+"{";
 for(var prop in styles){
  str+=prop.replace(/[A-Z]/g,function(item){
  return "-"+item.toLocaleLowerCase();
  })+":"+styles[prop]+";";
 }
 str+="}"
 styleSheet.insertRule(str,styleSheet.cssRules.length);
 }
 static getIdElem(elem,obj){
 if(elem.id) obj[elem.id]=elem;
 if(elem.children.length===0) return obj;
 for(let i=0;i<elem.children.length;i++){
  Utils.getIdElem(elem.children[i],obj);
 }
 }
}

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