用JS完成一个简单的省市二级联动

//省市二级联动   JS里边不能错 错就直接报错

var citys = new Array(4);

 citys[0]=new Array("静海区","塘沽区","南开区");

 citys[1]=new Array("石家庄","邯郸","邢台","廊坊","张家口","后北口");

 citys[2]=new Array("石景山","大兴","通州","密云","昌平","房山");

 citys[3]=new Array("郑州","开封","洛阳","驻马店","安阳");

function change(value){
var city = document.getElementById("city");
for(var i = city.options.length;i>0;i--){
city.options[i] = null;
}

for(var i = 0;i<citys.length;i++){
if(value==i){
for(var j = 0;j<citys[i].length;j++){
//alert(citys[i][j]);
var opEl = document.createElement("option");
var ctn = document.createTextNode(citys[i][j]);
opEl.appendChild(ctn);
city.appendChild(opEl);
}
}
}

}