原生JavaScript实现自定义下拉选择组件

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>select</title>
</head>
<body>
  <script type="module">
    import Main from './js/Main.js';
    //参数为false时，选择框不可点击；为true时，选择框可使用
    let main=new Main(true);
    main.appendTo("body");
  </script>
</body>
</html>

import Utils from './Utils.js';
export default class Main{
  static styles=false;
  listPrep;
  constructor(state){
    //state控制下拉框是否可点击
    this.state=state;
    this.elem=this.createE();
  }
  createE(){
    if(this.elem) return this.elem;
    let div=Utils.createE("div");
    div.className="guestsNum";
    div.innerHTML=`<span>人数未定</span><i></i>
    <div class="dropDownContainer none" id="dropDownContainer">
      <div class="dropDownItem clearfix">
        <span>每间</span>
        <div class="dropDownSelect">
          <div class="dropDownCont"><span id="adultNum">2 成人</span><i></i></div>
          <ul class="dropDownList" tag="adult">${this.setDropDownList("adult")}</ul>
        </div>
        <div class="dropDownSelect">
          <div class="dropDownCont"><span id="childrenNum">0 儿童</span><i></i></div>
          <ul class="dropDownList" tag="children"><li>0</li>${this.setDropDownList("children")}</ul>
        </div>
      </div>
      <div class="dropDownItem clearfix none" id="ItemAge"></div>
      <div class="dropDownBottom clearfix">
        ${this.state?'':'<em class="dropDownTips">请优先选择日期，以便查询实时价格。</em>'}
        ${this.state?'<a class="dropDownBtn" id="dropDownBtn" href="javascript:void(0)" rel="external nofollow" rel="external nofollow" >确认</a>':'<a class="dropDownBtn disabled" href="javascript:void(0)" rel="external nofollow" rel="external nofollow" >确认</a>'}
      </div>
    </div>`;
    //设置样式,因为样式只设置一次就好，不需要实例化，所以使用静态方法
    Main.setStyles();
    //获取元素
    Utils.getIdElem(div,this);
    //监听div的点击事件
    div.addEventListener("click",(e)=>this.guestsNumClickHandler(e));
    //如果state为true，下拉框监听点击事件
    if(this.state) this.dropDownContainer.addEventListener("click",e=>this.dropDownContainerClick(e));
    //document监听点击事件，隐藏下拉框
    document.addEventListener("click",e=>this.documentClick(e));
    return div;
  }
  appendTo(parent){
    Utils.appendTo(this.elem,parent);
  }
  guestsNumClickHandler(e){
    //如果下拉框是显示状态，则直接跳出，避免重复操作
    if(!Utils.hasClass(this.dropDownContainer,"none")) return;
    //如果点击的不是guestsNum，直接跳出，避免事件冒泡
    if(e.target.nodeName!=="SPAN"&&e.target.nodeName!=="I"&&!Utils.hasClass(e.target,"guestsNum")) return;
    //给div添加聚集样式
    Utils.addClass(this.elem,"focus");
    //将dropDownContainer显示
    Utils.removeClass(this.dropDownContainer,"none");
  }
  dropDownContainerClick(e){
    if(e.target.nodeName==="LI"){
      //点击ul选择列表
      this.dropDownListClick(e);
    }
    else if(e.target.id==="dropDownBtn"){
      //点击确认按钮
      this.dropDownBtnClick();
    }
    else if(e.target.nodeName==="SPAN" || e.target.nodeName==="I") {
      //点击span或者i标签时，将它们的父元素div作为参数
      this.dropDownSelectClick(e.target.parentElement);
    }
    else if(Utils.hasClass(e.target,"dropDownCont")){
      //点击div选择框时，将div作为参数
      this.dropDownSelectClick(e.target);
    }
    else {
      //点击下拉框内其它位置时，让当前的ul列表隐藏
      if(this.listPrep) this.listPrep.style.display="none";
    }
  }
  dropDownSelectClick(div){
    //隐藏掉上一个显示的ul列表
    if(this.listPrep) this.listPrep.style.display="none";
    //当前点击的ul列表赋值给this.listPrep
    this.listPrep=div.nextElementSibling;
    //将当前点击的ul列表显示
    this.listPrep.style.display="block";
  }
  dropDownListClick(e){
    //获取当前点击的ul的tag属性值
    let tag=this.listPrep.getAttribute("tag");
    let unit="";
    switch (tag){
      case "adult": unit="成人";break;
      case "children": 
        unit="儿童";
        let txt=Number(e.target.innerText);
        //根据li的数值，自动创建下面的年龄选择框
        this.setDropDownItemAge(txt);
        break;
      case "age": unit="岁";break;
    }
    //将选择的li的值，显示出来
    this.listPrep.previousElementSibling.firstElementChild.textContent=e.target.innerText+" "+unit;
    //显示完成后，将当前显示的ul隐藏
    this.listPrep.style.display="none";
  }
  setDropDownItemAge(txt){
    let str="<span>儿童年龄</span>";
    if(txt===0){
      //如果是0，则年龄选择框不显示
      this.ItemAge.style.display="none";
    }else{
      this.ItemAge.style.display="block";
      //循环选择的数值，创建年龄选择框
      for(let i=0;i<txt;i++){
        str+=`<div class="dropDownSelect">
        <div class="dropDownCont"><span><1岁</span><i></i></div>
        <ul class="dropDownList" tag="age"><li><1</li>${this.setDropDownList("age")}</ul>
      </div>`;
      }
      this.ItemAge.innerHTML=str;
    }
  }
  dropDownBtnClick(){
    //将选择的内容显示在最上方的select框内
    let resultStr=this.adultNum.innerText.replace(/\s/g,"")+" "+this.childrenNum.innerText.replace(/\s/g,"");
    this.elem.firstElementChild.textContent=resultStr;
    //隐藏dropDownContainer
    this.dropDownContainerHide();
  }
  documentClick(e){
    //避免事件冒泡
    if(e.target!==document.documentElement && e.target!==document.body) return;
    //隐藏dropDownContainer
    this.dropDownContainerHide();
  }
  dropDownContainerHide(){
    //div去掉聚集状态
    Utils.removeClass(this.elem,"focus");
    //dropDownContainer隐藏
    Utils.addClass(this.dropDownContainer,"none");
    //隐藏当前显示的ul列表
    if(this.listPrep) this.listPrep.style.display="none";
  }
  setDropDownList(type){
    //创建ul下拉列表内容
    let li="";
    let max=0;
    switch (type){
      case "adult": max=8;break;
      case "children": max=5;break;
      case "age": max=18;break;
    }
    for(let i=1;i<max;i++){
      li+="<li>"+i+"</li>";
    }
    return li;
  }
  static setStyles(){
    if(Main.styles) return;
    Main.style=true;
    Utils.insertCss(".guestsNum",{
      width:"108px",
      height:"34px",
      padding:"0px 12px",
      border:"1px solid #ccc",
      borderRadius:"3px",
      position:"relative",
      fontSize:"14px",
      color:"#666",
      userSelect:"none",
    })
    Utils.insertCss(".guestsNum.focus",{
      borderColor:"#ffa800",
      boxShadow:"0 0 4px #ffa800"
    })
    Utils.insertCss(".guestsNum>span",{
      lineHeight:"34px"
    })
    Utils.insertCss(".guestsNum>i",{
      display:"inline-block",
      width:"16px",
      height:"16px",
      backgroundImage:"url(./image/user.jpg)",
      float:"right",
      margin:"8px 0px 0px 10px"
    })
    Utils.insertCss(".dropDownContainer",{
      border: "1px solid #ffa800",
      borderRadius: "4px",
      boxShadow: "0 0 4px #ffa800",
      backgroundColor: "#fff",
      padding: "20px 15px",
      width: "480px",
      fontSize:"12px",
      position:"absolute",
      left:"0px",
      top:"35px",
    })
    Utils.insertCss(".dropDownItem",{
      marginBottom:"12px"
    })
    Utils.insertCss(".dropDownItem>span",{
      display:"block",
      width:"60px",
      lineHeight:"28px",
      float:"left",
    })
    Utils.insertCss(".dropDownSelect",{
      width:"90px",
      height:"30px",
      marginRight:"10px",
      float:"left",
      position:"relative"
    })
    Utils.insertCss(".dropDownCont",{
      border:"1px solid #ccc",
      borderRadius:"3px",
      height:"12px",
      padding:"6px 8px 10px",
    })
    Utils.insertCss(".dropDownCont>span",{
      display:"inline-block",
      width:"53px",
      height:"14px",
      lineHeight:"14px",
      borderRight:"1px solid #ccc"
    })
    Utils.insertCss(".dropDownCont>i",{
      display:"inline-block",
      width:"0px",
      height:"0px",
      border:"5px solid #c6c6c6",
      borderColor:"#c6c6c6 transparent transparent",
      margin: "6px 0px 0px 4px",
      float: "right"
    })
    Utils.insertCss(".dropDownList",{
      listStyle:"none",
      padding:"0px",
      margin:"0px",
      width:"88px",
      maxHeight:"200px",
      overflow:"auto",
      cursor:"pointer",
      border:"1px solid #ccc",
      backgroundColor:"#fff",
      borderRadius:"4px",
      position:"absolute",
      left:"0px",
      top:"30px",
      zIndex:"2",
      boxShadow: "1px 1px 3px rgba(0,0,0,.1)",
      display:"none"
    })
    Utils.insertCss(".dropDownList>li",{
      lineHeight:"28px",
      paddingLeft:"8px",
    })
    Utils.insertCss(".dropDownList>li:hover",{
      background:"#f4f4f4"
    })
    Utils.insertCss(".dropDownBottom",{
      borderTop:"1px solid #ccc",
      marginTop:"20px",
      paddingTop:"20px"
    })
    Utils.insertCss(".dropDownTips",{
      fontStyle:"normal",
      fontSize: "12px",
      color: "#ef523d",
      lineHeight:"28px"
    })
    Utils.insertCss(".dropDownBtn",{
      textDecoration:"none",
      float: "right",
      display: "inline-block",
      padding: "2px 22px",
      backgroundColor: "#ffb200",
      borderRadius: "4px",
      fontSize: "14px",
      lineHeight: "24px",
      color: "#fff",
    })
    Utils.insertCss(".dropDownBtn.disabled",{
      backgroundColor: "#efefef",
      color: "#999"
    })
    Utils.insertCss(".clearfix:after",{
      content:"\".\"",
      display:"block",
      overflow:"hidden",
      visibility:"hidden",
      clear:"both",
      height:"0px"
    })
    Utils.insertCss(".none",{
      display:"none"
    })
  }
}

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);
    }
  }
  static addClass(elem,className){
    let arr=(elem.className+" "+className).match(/\S+/g);
    arr=arr.filter((item,index)=>arr.indexOf(item,index+1)<0)
    elem.className=arr.join(" ");
  }
  static removeClass(elem,className){
    if(!elem.className) return;
    let arr=elem.className.match(/\S+/g);
    let arr1=className.match(/\S+/g);
    arr1.forEach(item=>{
      arr=arr.filter(t=>t!==item)
    })
    elem.className=arr.join(" ");
  }
  static hasClass(elem,className){
    if(!elem.className) return false;
    let arr=elem.className.match(/\S+/g);
    let arr1=className.match(/\S+/g);
    let res;
    arr1.forEach(item=>{
      res= arr.some(it=>it===item)
    })
    return res;
  }
}