刷新的时候，第一个省份8个市区都跳出来，要选第二个开始才能生效

来源：7-8 编程练习

慕标0359786

2019-12-20 14:53:14

function address(){
    var sheng=document.getElementById("sheng");
    var shi=document.getElementById("shi");
    var shengArray=["北京市","天津市","河北省","河南省"];
    var shiArray=["朝阳区","西城区","西青区","武清区","石家庄","邯郸市","郑州市","开封市"];
    selectAdd(sheng,shengArray);
    selectAdd(shi,shiArray);
}
function selectAdd(obj,name){
		for(var i in name){
			obj.options.add(new Option(name[i],name[i]));
		}  
}
function linkage(){
	var sheng=document.getElementById("sheng");
    var shi=document.getElementById("shi");
	//获取到省份的value值
	var sheng1 = sheng.value;
	//创建城区数组
	var beijinArray=["朝阳区","西城区"];
	var tianjinArray=["西青区","武青区"];
	var hebeiArray=["石家庄","邯郸市"];
	var henanArray=["郑州市","开封市"];
	//判断省份
	if(sheng1=="北京市"){
		shi.options.length=0;
		selectAdd(shi,beijinArray);
		
	}else if(sheng1=="天津市"){
		shi.options.length=0;
		
			selectAdd(shi,tianjinArray);
		
	}else if(sheng1=="河北省"){
		shi.options.length=0;
		
			selectAdd(shi,hebeiArray);
		
	}else{
		shi.options.length=0;
		
			selectAdd(shi,henanArray);
		
	}

}

<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
<title>Document</title>
    <script type="text/javascript" src="index.js"></script>
</head>
<body onload="address()">
<form>
省份：
   <select name="sheng" id="sheng" onchange="linkage()"></select>
市/区：
   <select name="shi" id="shi" onchange="linkage()"></select>
</form>
</body>
</html>

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