js 实现简单的三级联动

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声明：只为学习交流使用，记得当时是从开源中国上看的，如有侵犯权利可联系我删除，并再次感谢原作者

<!DOCTYPE html>

<html>

<head>
<meta charset="utf-8">
<title>js 简单实现三级联动</title>
</head>

<body>
省：
<select style="width: 100px;" id="pre" onchange="chg(this);">
<option value="-1">请选择</option>
</select>
市：
<select style="width: 100px;" id="city" onchange="chg2(this)" ;></select>
区：
<select style="width: 100px;" id="area"></select>
</body>
<script>
//声明省
var pres = ["北京", "上海", "山东"]; //直接声明Array
//声明市
var cities = [
["东城", "昌平", "海淀"],
["浦东", "高区"],
["济南", "青岛"]
];

var areas = [
[
["东城1", "东城2", "东城3"],
["昌平1", "昌平2", "昌平3"],
["海淀1", "海淀2", "海淀3"]
],
[
["浦东1", "浦东2", "浦东3"],
["高区1", "高区2", "高区3"]
],
[
["济南1", "济南2"],
["青岛1", "青岛2"]
]
]
//设置一个省的公共下标
var pIndex = -1;

var preEle = document.getElementById("pre");
var cityEle = document.getElementById("city");
var areaEle = document.getElementById("area");

//先设置省的值
for (var i = 0; i < pres.length; i++) {
//声明option.<option value="pres[i]">Pres[i]</option>
var op = new Option(pres[i], i);
//添加
preEle.options.add(op);
}

function chg(obj) {

if (obj.value == -1) {

cityEle.options.length = 0;
areaEle.options.length = 0;
}
//获取值
var val = obj.value;
pIndex = obj.value;

//获取ctiry
var cs = cities[val];
//获取默认区
var as = areas[val][0];

//先清空市
cityEle.options.length = 0;
areaEle.options.length = 0;

for (var i = 0; i < cs.length; i++) {
var op = new Option(cs[i], i);
cityEle.options.add(op);
}

for (var i = 0; i < as.length; i++) {

var op = new Option(as[i], i);

areaEle.options.add(op);
}
}

function chg2(obj) {

var val = obj.selectedIndex;

var as = areas[pIndex][val];

areaEle.options.length = 0;
for (var i = 0; i < as.length; i++) {

var op = new Option(as[i], i);

areaEle.options.add(op);
}
}
</script>

</html>

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