利用jquery修改下列代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Document</title>
</head>
<body>
选择城市：
<select name="" id="shengs">
<option value="请选择省份">请选择省份</option>
</select>
<select name="" id="shi">
<option value="请选择城市">请选择城市</option>
</select>
</body>
<style>
</style>
<script>
var sheng = new Array();
sheng["辽宁省"] = ["沈阳市", "大连市", "鞍山市", "抚顺市", "本溪市", "丹东市"];
sheng["吉林省"] = ["长春市", "吉林市", "四平市", "辽源市", "通化市", "白山市"];
sheng["黑龙江省"] = ["哈尔滨市", "牡丹江市", "齐齐哈尔市", "大庆市", "鸡西市", "佳木斯"];
var oSheng = document.getElementById("shengs");
var oCity = document.getElementById("shi");
for (var i in sheng) {
oSheng.add(new Option(i, i), null)
}
oSheng.onchange = function () {
oCity.length = 0;
var oSelect = oSheng.value;
for (var j in sheng[oSelect]) {
oCity.add(new Option(sheng[oSelect][j], sheng[oSelect][j]), null)
}
}
</script>
</html>
