为什么这个递归方法在IE中会中断？使用JSON

Question

在使用以下代码时，它可以在除IE之外的所有浏览器中运行，在IE中，它返回一个错误，指出行'if(dataitem.sub !== null)‘为空或未定义。我故意将JSON对象的sub属性设置为null，这样我就可以测试它，并确保有一个值与那个‘sub’属性相关联。只有IE在所有版本中都会中断。

            createDropDownCode: function(arr){
            // loop through li's of primary menu
            that.find("li").each(function(idx){

                $(this).append( menusort(arr.menu[idx].sub) );

                $('#PrimNav div.menu').hide();

                function menusort(data){
                    if(data !== null)
                        var html = "<div class='menu'><ul>";    

                    var data_count = 0;

                    for(item in data){

                        data.length-1 == data_count ? html += "<li class='last'>" : html += "<li>";

                        if(data[item].sub !== null){
                            if(typeof(data[item].sub) === 'object'){

                                html += "<a href='" + data[item].link + "'><span>" + data[item].name + "</span></a>";

                                if($.isArray(data[item].sub)){
                                    html += menusort(data[item].sub);
                                }
                            }
                        }

                        html += "</li>"
                        data_count += 1;

                    }

                    if(data !== null)
                        html += "</ul></div>";

                    return html;
                }

JSON传递给了'createDropDownCode‘函数....

var JSON = {
    menu: [
        {id: '0',sub: [
            {name: 'lorem ipsum 0-0',link: '0-0', sub: null},
            {name: 'lorem ipsum 0-1',link: '0-1', sub: null},
            {name: 'lorem ipsum 0-2',link: '0-2', sub: null}
            ]
        },
        {id: '1',sub: null},
        {id: '2',sub: [
            {name: 'lorem ipsum 2-0',link: '2-0', sub: null},
            {name: 'lorem ipsum 2-1',link: '2-1', sub: null},
            {name: 'lorem ipsum 2-2',link: '2-2', sub: [
                {name: 'lorem ipsum 2-2-0',link: '2-2-0', sub: null},
                {name: 'lorem ipsum 2-2-1',link: '2-2-1', sub: null},
                {name: 'lorem ipsum 2-2-2',link: '2-2-2', sub: [
                    {name: 'lorem ipsum 2-2-2-0',link: '2-2-2-0', sub: null},
                    {name: 'lorem ipsum 2-2-2-1',link: '2-2-2-1', sub: null},
                    {name: 'lorem ipsum 2-2-2-2',link: '2-2-2-2', sub: null},
                    {name: 'lorem ipsum 2-2-2-3',link: '2-2-2-3', sub: null}
                ]},
                {name: 'lorem ipsum 2-2-3',link: '2-2-3', sub: null},
                {name: 'lorem ipsum 2-2-4',link: '2-2-4', sub: null},
                {name: 'lorem ipsum 2-2-5',link: '2-2-5', sub: null},
                {name: 'lorem ipsum 2-2-6',link: '2-2-6', sub: null}
            ]},
            {name: 'lorem ipsum 2-3',link: '2-3', sub: [
                {name: 'lorem ipsum 2-3-0',link: '2-3-0', sub: null},
                {name: 'lorem ipsum 2-3-1',link: '2-3-1', sub: null},
                {name: 'lorem ipsum 2-3-2',link: '2-3-2', sub: [
                    {name: 'lorem ipsum 2-3-2-0',link: '2-3-2-0', sub: null},
                    {name: 'lorem ipsum 2-3-2-1',link: '2-3-2-1', sub: null},
                    {name: 'lorem ipsum 2-3-2-2',link: '2-3-2-2', sub: null},
                    {name: 'lorem ipsum 2-3-2-3',link: '2-3-2-3', sub: null}
                ]},
                {name: 'lorem ipsum 2-2-6',link: '2-3-3', sub: null}
            ]},
            {name: 'lorem ipsum 2-4',link: '2-4', sub: null},
            {name: 'lorem ipsum 2-5',link: '2-5', sub: null}
            ]
        },
        {id: '3',sub: null},
        {id: '4',sub: null},
        {id: '5',sub: null}
        ]
    }

Answer 1

在JSON数据中，尝试使用false而不是null，在我看来，对象类型比较有点多。

if(data[item].sub) {

    html += "<a href='" + data[item].link + "'><span>" + data[item].name + "</span></a>";

    if($.isArray(data[item].sub)) {
        html += menusort(data[item].sub);
    }
}

编辑:好的，这不是答案。正如我在上面的评论中所说的，请在http://jsfiddle.net上发布一个工作(或不工作；)的示例。