原生js实现三级联动下拉框

HTML部分

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>三级联动</title>
    <style>
      select {
        width: 200px;
        margin-right: 10px;
      }
    </style>
  </head>
  <body>
    <form action="">
      <select name="province" id="s1">
        <option value="">请选择省</option> </select
      >省
      <select name="city" id="s2" disabled="true">
        <option value="">请选择市</option> </select
      >市
      <select name="county" id="s3" disabled="true">
        <option value="">请选择区县</option> </select
      >县
    </form>
    <script src="./address.js"></script>
  </body>
</html>

JS部分

const forms = document.forms[0];
      for (let i = 0; i < data.length; i++) {
        let opt = document.createElement("option");
        opt.innerHTML = data[i].value;
        forms.province.appendChild(opt);
      }
      //省份发生改变时候触发的方法
      forms.province.onchange = function () {
        //根据下标判断当前是否选择了省份
        if (forms.province.selectedIndex !== 0) {
          forms.city.innerHTML="<option>请选择市</option>"
          forms.county.innerHTML="<option>请选择区县</option>"
          forms.city.disabled = false;
          let currentCity = [];
          for (let i = 0; i < data.length; i++) {
            if (data[i].value === forms.province.value) {
              currentCity = data[i].children;
            }
          }
          for(let i=0; i<currentCity.length; i++){
            let opt =document.createElement("option")
            opt.innerHTML=currentCity[i].value
            forms.city.appendChild(opt)
          }
        } else {
          forms.city.disabled=true
          forms.county.disabled=true
          forms.city.innerHTML="<option>请选择市</option>"
          forms.county.innerHTML="<option>请选择区县</option>"
        }
      };
      forms.city.onchange=function(){
        if (forms.city.selectedIndex!=0) {
          forms.county.innerHTML="<option>请选择区县</option>"
          forms.county.disabled=false
          let currentCity=[]
          let currentCounty=[]
          for (let i = 0; i < data.length; i++) {
            for(let j=0; j<data[i].children.length; j++){
              if (data[i].children[j].value== forms.city.value) {
                currentCounty=data[i].children[j].children
              }
            }
          }
          for(let i=0; i<currentCounty.length; i++){
            let opt=document.createElement("option")
            opt.innerHTML=currentCounty[i].value
            forms.county.appendChild(opt)
          }
        }else{
          forms.county.disabled=true
          forms.county.innerHTML="<option>请选择区县</option>"
        }
      }

国家的省市县JS文件大家可以在https://github.com/466879168/examples/blob/master/%E4%B8%89%E7%BA%A7%E8%81%94%E5%8A%A8/address.js里面查看下载

原生js实现三级联动下拉框

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