javascript jQuery ajax json 响应的长度未定义且数据不正确
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jQuery ajax json response has length undefined and incorrect data
提问by Dexter
I'm trying to grab a dictionary object which is converted to json object in server side, (along with correct content-type header), but for some reason, even though I can access part of the data, other parts don't show up and json object in jquery has length equal to 0.
我正在尝试获取一个字典对象，该对象在服务器端转换为 json 对象（以及正确的内容类型标头），但出于某种原因，即使我可以访问部分数据，其他部分也没有显示jquery 中的 up 和 json 对象的长度等于 0。
Here is my jquery call:
这是我的 jquery 调用：
$.ajax({
type : "POST",
url : cl._url,
//data : 'text='+text,
data: "{}",
contentType: "application/json; charset=utf-8",
dataType : "json",
error : function(XHR, status, error) {
alert("There was an error processing the request.\n\n"+XHR.responseText);
},
success : function(json){
if (!json.length) {
alert('There are no incorrectly spelled words...'+json[0]+ ' ' + json.length);
} else {
// highlight bad words
}
cl.$container.html(html);
// execute callback function, if any
(callback != undefined) && callback();
}
});
I usually get the alert box with this code, and json[0] prints out 99 as expected. But json.length is "undefined". So in a sense, the json returned is right but my code will not detect it and use it.
我通常会收到带有此代码的警报框，并且 json[0] 会按预期打印出 99。但是 json.length 是“未定义的”。所以从某种意义上说，返回的 json 是正确的，但我的代码不会检测到它并使用它。
When I go directly to my ashx page where my json data is printed on the screen, I get this json object:
当我直接进入我的 json 数据打印在屏幕上的 ashx 页面时，我得到了这个 json 对象：
{"id":1,"json":[5,10,15,20],"0":"99"}
Just a sample json output. So how come json.length is not 3???
只是一个示例 json 输出。那么 json.length 怎么不是 3 ？？？
UPDATE: So I changed my asp.net code, from Dictionary to List, and then added the same values. And suddenly, length is functioning now. ?!?!?! So objects don't have lengths in javascript?
更新：所以我将我的 asp.net 代码从字典更改为列表，然后添加了相同的值。突然之间，长度现在起作用了。？！？！？！所以对象在javascript中没有长度？
回答by Quentin
Objects don't have a length property unless you give them one. Arrays do, but arrays are created with []not {}.
对象没有长度属性，除非你给它们一个。数组可以，但数组是用[]not创建的{}。
If you want to know how many properties an object has, you have to loop over them and count them:
如果你想知道一个对象有多少个属性，你必须遍历它们并计算它们：
var count = 0;
for (var foo in bar) {
if (bar.hasOwnProperty(foo) {
count++;
}
}
回答by 3coins
Best way to debug this is to inspect the response under Firebug console. See if you are even getting back a valid response.
调试此问题的最佳方法是检查 Firebug 控制台下的响应。看看你是否甚至得到了有效的回应。
回答by Jad Chahine
You can convert your object to JSONusing :
您可以将对象转换为JSON使用：
var jsonVariable= JSON.stringify(objectVariable);
var jsonVariableLength = jsonVariable.length ;
And print the length :
并打印长度：
alert('Length : ' + jsonVariableLength );
