https://blog.csdn.net/yanchenxi313761/article/details/79731900
<script>
var iNum1;
var iNum2;
var aProvince = ['湖北','江蘇','安徽'];
var aCity =[['武漢','黃岡','荊門'],['南京','無錫','鎮江'],['合肥','安慶','黃山']];
var aCountry =[[['武漢1','武漢2'],['黃岡1','黃岡2'],['荊門1','荊門2']],[['南京1','南京2'],['無錫1','無錫2'],['鎮江1','鎮江2']],[['合肥1','合肥2'],['安慶1','安慶2'],['黃山1','黃山2']]];
$(function () {
for(var i=0;i<aProvince.length;i++){
$('#selProvince').append('<option>'+aProvince[i]+'</option>');
};
$('#selProvince').change(function () {
$('#selCity').children().not(':eq(0)').remove();
$('#selCountry').children().not(':eq(0)').remove();
iNum1 = $(this).children('option:selected').index();
var aaCity = aCity[iNum1-1];
for(var j=0;j<aaCity.length;j++){
$('#selCity').append('<option>'+aaCity[j]+'</option>');
}
});
$('#selCity').change(function () {
$('#selCountry').children().not(':eq(0)').remove();
iNum2 = $(this).children('option:selected').index();
var aaCountry = aCountry[iNum1-1][iNum2-1];
for(var k=0;k<aaCountry.length;k++){
$('#selCountry').append('<option>'+aaCountry[k]+'</option>');
}
})
})
</script>
</head>
<body>
<select name="" id="selProvince">
<option value="">----請選擇----</option>
</select>
<select name="" id="selCity">
<option value="">----請選擇----</option>
</select>
<select name="" id="selCountry">
<option value="">----請選擇----</option>
</select>