JavaScript实现三级联动菜单效果

2019-11-19 15:46:50

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三级联动考察的应该是对于数据的处理，只要清楚其中的关系，再多几级都是一样的：

html部分：

<!DOCTYPE html><html><head>  <meta charset="utf-8" />  <title>3级联动菜单</title>  <script>    var region = {      广东:      {        "广州":["广州1","广州2","广州3"],        "珠海":["珠海1","珠海2","珠海3"],        "佛山":["佛山1"]      },      湖南:      {        "常德":["石门","桃源","临澧","汉寿"],        "益阳":["益阳1","益阳2","益阳3"]      }    }  </script></head>  <body>    <select id="province" onchange="change(this.value);">      <option>请选择省份</option>    </select>    <select id="city" onchange="countyChange(this.value);">      <option>请选择地市</option>    </select>    <select id="county">      <option>请选择县城</option>    </select>  <script src='test.js'></script>  </body></html>

js部分：

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;      }    }  }

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