请选择省份
 

 
  请选择地市
 

 
  请选择县城
 
 
 

var province = document.querySelector("#province");
 var city = document.querySelector("#city");
 var county = document.querySelector("#county");
 //二级联动不用定义你选的省份,直接用省份(key)来决定下面的市(value)值
 var provinceName = null;

 for (ele in region){
 var op = new Option(ele , ele , false , false); //new Option("文本","值",true,true).后面两个true分别表示默认被选中和有效
 //console.log(op);
 province.options[province.length] = op;
 }

 var change = function(src){
 city.innerHTML = "";
 if(src === '请选择省份'){
  var op = new Option('请选择地市' , '请选择地市' , false , false);
  city.options[0] = op;
 }else{
  for (index in region[src]){
  //console.log(index);
  var op = new Option(index , index , false , false);
  city.options[city.length] = op;
  }
 }
 //记住选择省份的值
 provinceName=src;
 countyChange(city.value)
 }

 var countyChange = function(src2){
 county.innerHTML = "";
 if(src2 === '请选择地市'){
  var op = new Option('请选择县城','请选择县城', false , false);
  county.options[0] = op;
 }else{
  for (index in region[provinceName][src2]){
  //console.log(index);
  var op = new Option(region[provinceName][src2][index] , region[provinceName][src2][index] , false , false);
  county.options[county.length] = op;
  }
 }
 }