二级联动省市的为什么单独代码没有问题但是放进项目就有错误

[animal_]

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<h2>非专利微信平台交流会签到</h2>
<b>【地点】：南京市</b>
<b style="float: right;margin-right: 10px">2016-01-14</b>
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<option>吉林省</option>
<option>辽宁省</option>
<option>山东省</option>
<option>吉林省</option>
<option>辽宁省</option>
<option>山东省</option>
<option>吉林省</option>
<option>辽宁省</option>
<option>山东省</option>
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// 1. 获取省份列表,绑定onchange事件
var provinceElement = document.getElementById("province");
provinceElement.onchange = function(){
// 清空城市列表
var cityElement = document.getElementById("city");
var opts = cityElement.getElementsByTagName("option");
for(var z=1;z<opts.length;z++){
cityElement.removeChild(opts[z]);
z--;
}
var provinceValue = provinceElement.value;
var cities;
switch (provinceValue){
case "吉林省":
cities = ["长春市","吉林市","松原市","四平市","通化市"];
break;
case "辽宁省":
cities = ["沈阳市","大连市","铁岭市","丹东市","锦州市"];
break;
case "山东省":
cities = ["济南市","青岛市","威海市","日照市","德州市"];
break;
case "吉林省":
cities = ["长春市","吉林市","松原市","四平市","通化市"];
break;
case "辽宁省":
cities = ["沈阳市","大连市","铁岭市","丹东市","锦州市"];
break;
case "山东省":
cities = ["济南市","青岛市","威海市","日照市","德州市"];
break;
case "吉林省":
cities = ["长春市","吉林市","松原市","四平市","通化市"];
break;
case "辽宁省":
cities = ["沈阳市","大连市","铁岭市","丹东市","锦州市"];
break;
case "山东省":
cities = ["济南市","青岛市","威海市","日照市","德州市"];
break;
}
for(var i=0;i<cities.length;i++){
var cityValue = cities[i];
var option = document.createElement("option");
var textNode = document.createTextNode(cityValue);
option.appendChild(textNode);
cityElement.appendChild(option);
}
}
</script>
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<option>请选择城市</option>
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[ideep]

var provinceValue = provinceElement.value; provinceElement.value是HTML元素数组。你怎么取它的值呀

[ideep]

<div id="province" <select id="province"