【发布时间】：2012-03-26 23:36:40
【问题描述】：
在使用下面的代码时，它可以在除 IE 之外的所有浏览器中运行，它会返回一个错误，指出行 'if(data[item].sub !== null)' 为 null 或未定义。我故意将 JSON 对象的子属性设置为 null，以便对此进行测试并确保存在与该“子”属性关联的值。所有版本中只有 IE 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 '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}
]
}
【问题讨论】：
-
为什么不写
if (data === null) return "";？ -
这一行是做什么的： data.length-1 == data_count ？ html += "
- " : html += "
- "; ?
-
Fabian，因为我正在使用 for...in 循环，我无法访问给定当前项目的变量，因此必须包含一个计数器以便我知道何时我在项目循环的末尾并向该项目添加一个类“last”。
-
@quinton 我明白了，但这是一种非常“hackish”的写作方式。乍一看，我不认为它是一个缩短的 if 语句。顺便问一下，我的回答对你有帮助吗？我刚刚有了另一个想法，您能否将您的代码的工作示例发布到jsfiddle.net？
-
我找到了答案，虽然它的响应不好，但 IE 出错了，这真的很简单而且很好。我需要做的就是确保我事先用'var'定义了'item'。所以 for(item in data) 变成 for(var item in data)。我还将在 for 循环内添加一个 hasOwnProperty 测试，以确保所有属性都属于该对象。
标签： javascript json internet-explorer recursion