麻烦老师检查下我的代码，谢谢～

来源：7-8 编程练习

Heijyu

2020-11-12 16:26:06

html代码部分如下：

<html>
	<head>
		<title></title>
		<script src="javaScript1.js" type="text/javascript" charset="utf-8" async defer></script>
	</head>
	<body onload = "address()">
		<form>
			 省份：
		         <!--  请在此补充代码 -->
			 <select name="province" id="province" onchange="linkage()"></select> 
			 市/区：
			 <!--  请在此补充代码 -->
			 <select name="city" id="city" onchange="linkage()"></select>

		</form>
	</body>
</html>

js代码部分如下：

function address(){
    /*请在此补充代码*/ 
    var proArr = ["Beijing", "Tianjin", "Hebei", "Henan"];
    var cityArr = ["Chaoyang", "Xichengqu", "Shijiazhuang", "Handan", "Xiqingqu", "Wuqingqu", "Zhengzhou", "Kaifeng"];
    var province = document.getElementById("province");
    var city = document.getElementById("city");
    selectAdd(province,proArr,proArr);
    selectAdd(city,cityArr, cityArr);
}
function selectAdd(obj,name,value){
	/*请在此补充代码*/  
	for(var i=0; i<=name.length; i++){
		obj.options.add(new Option(name[i],value[i]));
	}
}
function linkage(){
	/*请在此补充代码*/  
	var proArr = ["Beijing", "Tianjin", "Hebei", "Henan"];
    var cityArr = ["Chaoyang", "Xichengqu", "Shijiazhuang", "Handan", "Xiqingqu", "Wuqingqu", "Zhengzhou", "Kaifeng"];
    var province = document.getElementById("province");
    var city = document.getElementById("city");
    var str = province.value;
    var cityResArr;
    switch(str){
    	case "Beijing":
    		cityResArr = [cityArr[0],cityArr[1]];
    		break;
    	case "Tianjin":
    		cityResArr = [cityArr[4],cityArr[5]];
    		break;
    	case "Hebei":
    		cityResArr = [cityArr[2],cityArr[3]];
    		break;
    	case "Henan":
    		cityResArr = [cityArr[6],cityArr[7]];
    		break;
    }
    city.options.length = 0;
    selectAdd(city,cityResArr,cityResArr);
}