$.each()方法，其实挺不错的

例子为主

html主要代码

<div class="fl search">厂商：<select id="firms"><option>请选择</option></select> 品牌：<select id="brandmark"><option>请选择</option></select> 型号：<select id="type"><option>请选择</option></select>

js：

$(function(){

function init(obj){
return $(obj).html("<option>请选择</option>");
}
var goodsData = {
小米: {小米:"小米3,小米4",红米:"红米note,红米note2"},
苹果: {iphone:"iphone5,iphone6",ipad:"ipad1,ipad2"},
魅族: {魅族:"魅族1,魅族2",魅蓝:"魅蓝1,魅蓝note"}
};
var f = false;
var b = false;
var t = false;
$.each(goodsData,function(fs){
$('#firms').append("<option>"+fs+"</option>");

});
$('#firms').change(function(){
f = true;
init("#brandmark");
init("#type");
$.each(goodsData,function(fs,bo){

if($('#firms option:selected').text() == fs){
$.each(bo,function(bd,tp){
$('#brandmark').append("<option>"+bd+"</option>");
});
$('#brandmark').change(function(){
init("#type");
b = true;
$.each(bo,function(bd,tp){
if($('#brandmark option:selected').text() == bd){
$.each(tp.split(","),function(){
$('#type').append("<option>"+this+"</option>")
});
}
});
$('#type').change(function(){
t = true;
});
});
}
});
});
$('#searchBtn').click(function(){
if(f&&b&&t){
var str = "你选择的厂商:";
str += $('#firms option:selected').text();
str +="&nbsp;你选择的品牌：";
str += $('#brandmarkm option:selected').text();
str +="&nbsp;你选择的型号：";
str += $('#type option:selected').text();
$('.showdata').show().html(str);
}else if(f&&!b&&!t){
$('.showdata').show().html("请选择品牌和型号");
}else if(f&&b&&!t){
$('.showdata').show().html("请选择型号");
}else{
$('.showdata').show().html("请选择商品");
}
});
});