Scripts/Category.js

调用方法：

$(function () {    BindCategory();    //默认绑定文本框中的值    BindCategoryData($("#txtCategoryId").val());})

绑定三级联动（详情见：http://www.cnblogs.com/haozhenjie819/p/3887279.html）

function BindCategory() {    var $txtCategory = $("#txtCategoryId");    var _selectId = ["selBigClass", "selSmallClass", "selThreeClass"];    for (var i = 0; i < _selectId.length; i++) {        var select = document.createElement("select");        select.id = _selectId[i];        select.name = _selectId[i];        $txtCategory.parent().append(select);    }    var $selBigClass = $("#selBigClass");    var $selSmallClass = $("#selSmallClass");    var $selThreeClass = $("#selThreeClass");    $selSmallClass.hide();    $selThreeClass.hide();    $.getJSON("/Scripts/CategoryJson.js", function (json) {        var html = ['<option value="">请选择大类</option>'];        for (var key in json) {            if (json[key].pid == 0) {                html.push('<option value="' + json[key].id + '">' + json[key].name + '</option>');            }        }        //第一级类别        $selBigClass.empty().append(html.join('')).change(function () {            $txtCategory.val(this.value);            $selThreeClass.hide();            $selSmallClass.show();            var html = ['<option value="">请选择小类</option>'];            for (var data in json) {                if (json[data].pid == $("#selBigClass").val()) {                    html.push('<option value="' + json[data].id + '">' + json[data].name + '</option>');                }            }            //第二级类别            $selSmallClass.empty().append(html.join('')).change(function () {                $txtCategory.val(this.value);                               $selThreeClass.show();                var html = ['<option value="">请选择小类</option>'];                for (var data in json) {                    if (json[data].pid == $selSmallClass.val()) {                        html.push('<option value="' + json[data].id + '">' + json[data].name + '</option>');                    }                }                //第三级类别                $selThreeClass.empty().append(html.join('')).change(function () {                    $txtCategory.val(this.value);                });                //如果不存在第三级类别则隐藏第三级类别控件                if ($selThreeClass.get(0).options.length <= 1) {                    $selThreeClass.hide();                    return false;                }            });            //如果不存在第二级类别则隐藏第二级类别控件            if ($selSmallClass.get(0).options.length <= 1) {                $selSmallClass.hide();                return false;            }                   });    });};

根据参数显示默认值

var setBigClassTime;//绑定数据function BindCategoryData(CategoryId) {    if (document.getElementById("selBigClass") == null || document.getElementById("selBigClass").length <= 0)        setBigClassTime = setTimeout("BindCategoryData('" + CategoryId + "')", 200);    else        clearTimeout(setBigClassTime);    $.getJSON('/Scripts/CategoryJson.js', function (json) {        for (var key in json) {            if (json[key].id == CategoryId) {                json[key].id = CategoryId;                var str = json[key].itemvalue;                var _p = str.split("|")[2];                var _c = json[key].pid;                if (_p == _c) {                    if (_p != "") {                        $("#selBigClass").val(_p).change();                        $("#selSmallClass").val(CategoryId);                    }                    else {                        $("#selBigClass").val(CategoryId);                    }                }                else {                    $("#selBigClass").val(_p).change();                    $("#selSmallClass").val(_c).change();                    $("#selThreeClass").val(CategoryId).change();                }            }        }    });}

Scripts/CategoryJson.js（如何生成json数据详见：http://www.cnblogs.com/haozhenjie819/p/3601676.html）

[{ "id": 31, "name": "\u65b0\u95fb\u4e2d\u5fc3", "pid": 0, "itemvalue": "|0|" },{ "id": 59, "name": "\u52a0\u76df\u5408\u4f5c", "pid": 0, "itemvalue": "|0|" },{ "id": 65, "name": "\u4ea7\u54c1\u670d\u52a1", "pid": 0, "itemvalue": "|0|" },{ "id": 60, "name": "\u52a0\u76df\u987b\u77e5", "pid": 59, "itemvalue": "|0|59|" },{ "id": 61, "name": "\u52a0\u76df\u6d41\u7a0b", "pid": 59, "itemvalue": "|0|59|" },{ "id": 62, "name": "\u52a0\u76df\u533a\u57df", "pid": 59, "itemvalue": "|0|59|" },{ "id": 70, "name": "\u63a8\u8350\u670d\u52a1", "pid": 65, "itemvalue": "|0|65|" },{ "id": 71, "name": "\u8ba1\u8d39\u65b9\u5f0f", "pid": 65, "itemvalue": "|0|65|" },{ "id": 72, "name": "\u7528\u6237\u987b\u77e5", "pid": 65, "itemvalue": "|0|65|" },{ "id": 73, "name": "\u7981\u5bc4\u8303\u56f4", "pid": 65, "itemvalue": "|0|65|" },{ "id": 75, "name": "\u666e\u901a\u5feb\u9012", "pid": 70, "itemvalue": "|0|65|70|" },{ "id": 76, "name": "\u7279\u79cd\u5feb\u4ef6", "pid": 70, "itemvalue": "|0|65|70|" },{ "id": 77, "name": "\u9650\u65f6\u6d3e\u9001", "pid": 70, "itemvalue": "|0|65|70|" },{ "id": 78, "name": "\u4ee3\u6536\u8d37\u6b3e", "pid": 70, "itemvalue": "|0|65|70|" },{ "id": 79, "name": "\u4fdd\u4ef7\u670d\u52a1", "pid": 70, "itemvalue": "|0|65|70|" }, { "id": 80, "name": "\u4ee3\u7b7e\u56de\u5355", "pid": 70, "itemvalue": "|0|65|70|"}]

web页面（给hidden赋值，类别编号为75）

<html xmlns="http://www.w3.org/1999/xhtml"><head runat="server">    <title>三级联动</title>    <script src="/Scripts/jquery-1.4.1.min.js" type="text/javascript"></script>    <script src="/Scripts/Category.js" type="text/javascript"></script>  </head><body>    <form id="form1" runat="server">            <table>            <tr>                <td >新闻类别：</td>                <td > <input id="txtCategoryId" name="txtCategoryId" type="hidden" runat="server" value="75" /></td>            </tr>            </table>    </form>    </body></html>

效果图

 

 

 

 

 

 

 

涉及的知识点：【JavaScript split() 方法】返回值是一个字符串数组。