三级联动，前一个的值会确定下一个下拉列表的内容（以地区为例，地区不全）
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>三级联动</title>
</head>
<body>
<select id="province">
<option>请选择省</option>
</select>
<select id="city">
<option>请选择市</option>
</select>
<select id="region">
<option>请选择区（县）</option>
</select>
<script type="text/javascript">
var oPrivince = document.getElementById("province");
var oCity = document.getElementById("city");
var oRegion = document.getElementById("region");
oCity.disabled = true;
oRegion.disabled = true;
var province = [{'id':'1','name':'北京'}, //一级联动用数组存储，每一项都是json，加上id
{'id':'2','name':'上海'},
{'id':'3','name':'天津'},
{'id':'4','name':'河北'},
{'id':'5','name':'山东'},
{'id':'6','name':'广东'},];
var str1 = '';
for(var i = 0;i<province.length;i++)
{
var proArr = province[i];
str1 += '<option value='+proArr.id+'>'+proArr.name+'</option>'
}
oPrivince.innerHTML += str1;
var city = {"1":['101#北京'], //二级联动用json存储，属性对应一级联动的id
"2":['201#上海'],
"3":['301#天津'],
"4":['401#石家庄','402#保定','403#沧州','404#秦皇岛','405#邢台','406#唐山'],
"5":['501#济南','502#青岛','503#烟台','504#菏泽','505#威海','506#莱阳','507#济宁'],
"6":['601#广州','602#汕头','603#深圳','604#东莞','605#珠海','606#佛山','607#南海']};
oPrivince.onchange = function(){ //一级联动内容发生变动时触发
oCity.innerHTML = '<option>请选择市</option>'
oCity.disabled = false;
oRegion.innerHTML = '<option>请选择区（县）</option>'
oRegion.disabled = true;
var str2 ='';
var value1 = this.value;
var cityArr = city[value1]; //根据一级联动的value值，来匹配二级联动里的json的属性，将对应的属性值存到数组中
console.log(value1);
//对数组的每一项分割，取出想要的内容，加入到二级联动列表中
for(var i = 0;i<cityArr.length;i++)
{
var citySp = cityArr[i].split('#');
str2 += '<option value='+citySp[0]+'>'+citySp[1]+'</option>';
}
oCity.innerHTML += str2;
}
//三级联动和二级联动存储相同
var region = { "101":['朝阳区','海淀区','昌平区','大兴区','怀柔区','石景山区'],
"201":['上海1','上海2','上海3','上海4','上海5','上海6','上海7','上海8'],
"301":['天津1','天津2','天津3','天津4','天津5','天津6','天津7','天津8'],
"401":['石家庄1','石家庄2','石家庄3','石家庄4','石家庄5','石家庄6','石家庄7','石家庄8'],
"402":['保定1','保定2','保定3','保定4','保定5','保定6','保定7','保定8'],
"403":['沧州1','沧州2','沧州3','沧州4','沧州5','沧州6','沧州7','沧州8'],
"404":['秦皇岛1','秦皇岛2','秦皇岛3','秦皇岛4','秦皇岛5','秦皇岛6','秦皇岛7','秦皇岛8'],
"405":['邢台1','邢台2','邢台3','邢台4','邢台5','邢台6','邢台7','邢台8'],
"406":['唐山1','唐山2','唐山3','唐山4','唐山5','唐山6','唐山7','唐山8'],
"501":['济南1','济南2','济南3','济南4','济南5','济南6','济南7','济南8'],
"502":['青岛1','青岛2','青岛3','青岛4','青岛5','青岛6','青岛7','青岛8'],
"503":['烟台1','烟台2','烟台3','烟台4','烟台5','烟台6','烟台7','烟台8'],
"504":['菏泽1','菏泽2','菏泽3','菏泽4','菏泽5','菏泽6','菏泽7','菏泽8'],
"505":['威海1','威海2','威海3','威海4','威海5','威海6','威海7','威海8'],
"506":['莱阳1','莱阳2','莱阳3','莱阳4','莱阳5','莱阳6','莱阳7','莱阳8'],
"507":['济宁1','济宁2','济宁3','济宁4','济宁5','济宁6','济宁7','济宁8'],
"601":['广州1','广州2','广州3','广州4','广州5','广州6','广州7','广州8'],
"602":['汕头1','汕头2','汕头3','汕头4','汕头5','汕头6','汕头7','汕头8'],
"603":['深圳1','深圳2','深圳3','深圳4','深圳5','深圳6','深圳7','深圳8'],
"604":['东莞1','东莞2','东莞3','东莞4','东莞5','东莞6','东莞7','东莞8'],
"605":['珠海1','珠海2','珠海3','珠海4','珠海5','珠海6','珠海7','珠海8'],
"606":['佛山1','佛山2','佛山3','佛山4','佛山5','佛山6','佛山7','佛山8'],
"607":['南海1','南海2','南海3','南海4','南海5','南海6','南海7','南海8'],}
oCity.onchange = function(){
oRegion.innerHTML = '<option>请选择区（县）</option>'
oRegion.disabled = false;
var str3 = '';
value2 = this.value;
var regionArr = region[value2];
for(var i = 0 ;i<regionArr.length;i++)
{
str3 += '<option>'+regionArr[i]+'</option>'
}
oRegion.innerHTML += str3;
}
</script>
</body>
</html>