其中参数1是菜单结构：
菜单对象
var menu = [ {'val': '1', 'txt': 'value'}, {'val': '2 ->', 'menu': [ {'val': '2_1'}, {'val': '2_2'} ]}, {'val': '3 ->', 'menu': [ {'val': '3_1 ->', 'menu': [ {'val': '3_1_1'}, {'val': '3_1_2'} ]}, {'val': '3_2'} ]}, {'val': '4 ->', 'menu': [ {'val': '4_1 ->', 'menu': [ {'val': '4_1_1 ->', 'menu': [ {'val': '4_1_1_1'} ]} ]} ]}];
参数2是select的id集合(按顺序)：
var sel=["sel1","sel2","sel3","sel4","sel5"]
可设置默认值(按顺序)：
var val=["3 ->", "3_1 ->", "3_1_2"];
源码:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=gb2312" /><title>JavaScript 自定义多级联动下拉菜单</title><script type="text/javascript">var $ = function (id) { return "string" == typeof id ? document.getElementById(id) : id;};function addEventHandler(oTarget, sEventType, fnHandler) { if (oTarget.addEventListener) { oTarget.addEventListener(sEventType, fnHandler, false); } else if (oTarget.attachEvent) { oTarget.attachEvent("on" + sEventType, fnHandler); } else { oTarget["on" + sEventType] = fnHandler; }};function Each(arrList, fun){ for (var i = 0, len = arrList.length; i < len; i++) { fun(arrList[i], i); }};function GetOption(val, txt) { var op = document.createElement("OPTION"); op.value = val; op.innerHTML = txt; return op;};var Class = { create: function() { return function() { this.initialize.apply(this, arguments); } }}Object.extend = function(destination, source) { for (var property in source) { destination[property] = source[property]; } return destination;}var CascadeSelect = Class.create();CascadeSelect.prototype = { //select集合，菜单对象 initialize: function(arrSelects, arrMenu, options) { if(arrSelects.length <= 0 || arrMenu.lenght <= 0) return;//菜单对象 var oThis = this; this.Selects = [];//select集合 this.Menu = arrMenu;//菜单对象 this.SetOptions(options); this.Default = this.options.Default || []; this.ShowEmpty = !!this.options.ShowEmpty; this.EmptyText = this.options.EmptyText.toString(); //设置Selects集合和change事件 Each(arrSelects, function(o, i){ addEventHandler((oThis.Selects[i] = $(o)), "change", function(){ oThis.Set(i); }); }); this.ReSet(); }, //设置默认属性 SetOptions: function(options) { this.options = {//默认值 Default: [],//默认值(按顺序) ShowEmpty: false,//是否显示空值(位于第一个) EmptyText: "请选择"//空值显示文本(ShowEmpty为true时有效) }; Object.extend(this.options, options || {}); }, //初始化select ReSet: function() { this.SetSelect(this.Selects[0], this.Menu, this.Default.shift()); this.Set(0); }, //全部select设置 Set: function(index) { var menu = this.Menu //第一个select不需要处理所以从1开始 for(var i=1, len = this.Selects.length; i < len; i++){ if(menu.length > 0){ //获取菜单 var value = this.Selects[i-1].value; if(value!=""){ Each(menu, function(o){ if(o.val == value){ menu = o.menu || []; } }); } else { menu = []; } //设置菜单 if(i > index){ this.SetSelect(this.Selects[i], menu, this.Default.shift()); } } else { //没有数据 this.SetSelect(this.Selects[i], [], ""); } } //清空默认值 this.Default.length = 0; }, //select设置 SetSelect: function(oSel, menu, value) { oSel.options.length = 0; oSel.disabled = false; if(this.ShowEmpty){ oSel.appendChild(GetOption("", this.EmptyText)); } if(menu.length <= 0){ oSel.disabled = true; return; } Each(menu, function(o){ var op = GetOption(o.val, o.txt ? o.txt : o.val); op.selected = (value == op.value); oSel.appendChild(op); }); }, //添加菜单 Add: function(menu) { this.Menu[this.Menu.length] = menu; this.ReSet(); }, //删除菜单 Delete: function(index) { if(index < 0 || index >= this.Menu.length) return; for(var i = index, len = this.Menu.length - 1; i < len; i++){ this.Menu[i] = this.Menu[i + 1]; } this.Menu.pop() this.ReSet(); }};window.onload=function(){ var menu = [ {'val': '1', 'txt': 'value'}, {'val': '2 ->', 'menu': [ {'val': '2_1'}, {'val': '2_2'} ]}, {'val': '3 ->', 'menu': [ {'val': '3_1 ->', 'menu': [ {'val': '3_1_1'}, {'val': '3_1_2'} ]}, {'val': '3_2'} ]}, {'val': '4 ->', 'menu': [ {'val': '4_1 ->', 'menu': [ {'val': '4_1_1 ->', 'menu': [ {'val': '4_1_1_1'} ]} ]} ]} ]; var sel=["sel1", "sel2", "sel3", "sel4", "sel5"]; var val=["3 ->", "3_1 ->", "3_1_2"]; var cs = new CascadeSelect(sel, menu, { Default: val }); $("btnA").onclick=function(){cs.ShowEmpty=!cs.ShowEmpty;} $("btnB").onclick=function(){ cs.Add( {'val': '5 ->', 'menu': [ {'val': '5_1 ->', 'menu': [ {'val': '5_1_1 ->', 'menu': [ {'val': '5_1_1_1 ->', 'menu': [ {'val': '5_1_1_1_1'} ]} ]} ]} ]} ) } $("btnC").onclick=function(){ cs.Delete(3) }}</script><style type="text/css">.sel select{ width:100px;}</style></head><body><div class="sel"><select id="sel1"></select><select id="sel2"></select><select id="sel3"></select><select id="sel4"></select><select id="sel5"></select></div><br /><div><input id="btnA" type="button" value="显示/不显示空值" /><input id="btnB" type="button" value="添加菜单" /><input id="btnC" type="button" value="减少菜单" /></div></body></html>
转自:http://www.cnblogs.com/cloudgamer/archive/2008/06/24/1228736.html
黑色头发:http://heisetoufa.iteye.com/
相关资源：html+js实现地区三级联动下拉菜单
