blocks|key|1079011|text|既然它只是false和json对象，为什么不检查它是否是false，否则一定是json对象。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1079012|if(ret+==+false+%7C%7C+ret+==+"false")+{
++++//+json
}|code-block|syntax|javascript|1079013|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Since it's just false and json object, why don't you check whether it's false, otherwise it must be json.

<pre><code>if(ret == false || ret == "false") {
 // json
}
</code></pre>

blocks|key|1079088|text|如果您想显式地测试有效的JSON+(而不是没有返回值false)，那么可以使用here中描述的解析方法。|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1079089|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/questions/3710204/how-to-check-if-a-string-is-a-valid-json-string-in-javascript-without-using-try-c^0|Q|5|13|4|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]]|D|@$9|Q|A|R|1|S]]|E|$]]|$1|F|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

If you want to test explicitly for valid JSON (as opposed to the absence of the returned value <code>false</code>), then you can use a parsing approach as described <a href="https://stackoverflow.com/questions/3710204/how-to-check-if-a-string-is-a-valid-json-string-in-javascript-without-using-try-c">here</a>.

blocks|key|864561|text|如果字符串是JSON，那么jQuery.parseJSON()应该返回一个"+object“类型的对象，所以您只需要用typeof检查类型|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|864562|var+response=jQuery.parseJSON('response+from+server');
if(typeof+response+=='object')
{
++//+It+is+JSON
}
else
{
++if(response+===false)
++{
+++++//+the+response+was+a+string+"false",+parseJSON+will+convert+it+to+boolean+false
++}
++else
++{
++++//+the+response+was+something+else
++}
}|code-block|syntax|javascript|864563|entityMap^0|1N|6|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

jQuery.parseJSON() should return an object of type "object", if the string was JSON, so you only have to check the type with <code>typeof</code>

<pre><code>var response=jQuery.parseJSON('response from server');
if(typeof response =='object')
{
 // It is JSON
}
else
{
 if(response ===false)
 {
 // the response was a string "false", parseJSON will convert it to boolean false
 }
 else
 {
 // the response was something else
 }
}
</code></pre>

blocks|key|864634|text|The+chosen+solution实际上并不适合我，因为我得到了一个|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|864635|+++++"Unexpected+Token+<"+|code-block|syntax|javascript|864636|Chrome中的错误。这是因为一旦解析遇到未知字符，就会抛出错误。但是，如果您只通过ajax返回字符串值，那么有一种方法可以解决这个问题(如果您正在使用PHP或ASPX来处理ajax请求，并且可能根据条件返回JSON，这将非常有用)。|864637|解决方案非常简单，您可以执行以下操作来检查它是否是有效的JSON返回|864638|+++++++var+IS_JSON+=+true;
+++++++try
+++++++{
+++++++++++++++var+json+=+$.parseJSON(msg);
+++++++}
+++++++catch(err)
+++++++{
+++++++++++++++IS_JSON+=+false;
+++++++}++++++++++++++++|864639|正如我之前所说的，如果您从AJAX请求中返回字符串类型的内容，或者如果您返回的是混合类型，这就是解决方案。|864640|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/4295670/662581^0|0|J|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Y|8|@]|9|@$A|Z|B|10|1|11]]|C|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|14|8|@]|9|@]|C|$]]|$1|M|3|N|5|F|7|15|8|@]|9|@]|C|$G|H]]|$1|O|3|P|5|6|7|16|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|R|$S|$5|T|U|V|C|$W|X]]]]

<a href="https://stackoverflow.com/a/4295670/662581">The chosen solution</a> doesn't actually work for me because I get a 

<pre><code> "Unexpected Token &lt;" 
</code></pre>

error in Chrome. This is because the error is thrown as soon as the parse comes across and unknown character. However, there is a way around this if you are returning only string values through ajax (which can be fairly useful if you are using PHP or ASPX to process ajax requests and might or might not return JSON depending on conditions)

The solution is quite simple, you can do the following to check if it was a valid JSON return

<pre><code> var IS_JSON = true;
 try
 {
 var json = $.parseJSON(msg);
 }
 catch(err)
 {
 IS_JSON = false;
 } 
</code></pre>

As I have said before, this is the solution for if you are either returning string type stuff from your AJAX request or if you are returning mixed type.

blocks|key|1079280|text|我知道这个帖子已经被回复了，但来到这里并没有真正解决我的问题，我在其他地方找到了这个函数。也许来这里的人会发现它对他们有一些用处；|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1079281|function+getClass(obj)+{
++if+(typeof+obj+===+"undefined")
++++return+"undefined";
++if+(obj+===+null)
++++return+"null";
++return+Object.prototype.toString.call(obj)
++++.match(/%5E\[object\s(.*)\]$/)[1];
}|code-block|syntax|javascript|1079282|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I know this thread has been answered already, but coming here didn't really solve my problems, I found this function somewhere else.
maybe someone coming here will find it to be of some use to them;

<pre><code>function getClass(obj) {
 if (typeof obj === "undefined")
 return "undefined";
 if (obj === null)
 return "null";
 return Object.prototype.toString.call(obj)
 .match(/^\[object\s(.*)\]$/)[1];
}
</code></pre>

blocks|key|1079324|text|var+data+=+'json+string+?';
var+jdata+=+null;
try
{
++++jdata+=+$.parseJSON(data);++
}catch(e)
{}

if(jdata)
{
//use+jdata
}else
{
//use+data
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1079325|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var data = 'json string ?';
var jdata = null;
try
{
 jdata = $.parseJSON(data); 
}catch(e)
{}

if(jdata)
{
//use jdata
}else
{
//use data
}
</code></pre>

blocks|key|1079346|text|如果您有jQuery，请使用isPlainObject。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1079347|if+($.isPlainObject(my_var))+{}|code-block|syntax|javascript|1079348|entityMap|0|LINK|mutability|MUTABLE|url|http://api.jquery.com/jQuery.isPlainObject/^0|E|D|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

If you have jQuery, use <a href="http://api.jquery.com/jQuery.isPlainObject/">isPlainObject</a>.

<pre><code>if ($.isPlainObject(my_var)) {}
</code></pre>

blocks|key|1079415|text|解决方案3(最快方式)|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1079416|/**
+*+@param+Object
+*+@returns+boolean
+*/
function+isJSON+(something)+{
++++if+(typeof+something+!=+'string')
++++++++something+=+JSON.stringify(something);

++++try+{
++++++++JSON.parse(something);
++++++++return+true;
++++}+catch+(e)+{
++++++++return+false;
++++}
}|code-block|syntax|javascript|1079417|您可以使用它：|1079418|var+myJson+=+[{"user":"chofoteddy"},+{"user":"bart"}];
isJSON(myJson);+//+true|1079419|1079420|验证对象是JSON类型还是数组类型的最佳方法如下：|1079421|var+a+=+[],
++++o+=+{};|1079422|解决方案1|1079423|toString.call(o)+===+'[object+Object]';+//+true
toString.call(a)+===+'[object+Array]';+//+true|1079424|解决方案2|1079425|a.constructor.name+===+'Array';+//+true
o.constructor.name+===+'Object';+//+true|1079426|但是，严格地说，数组是JSON语法的一部分。因此，以下两个示例是JSON响应的一部分：|1079427|console.log(response);+//+{"message":+"success"}
console.log(response);+//+{"user":+"bart",+"id":3}|1079428|和：|1079429|console.log(response);+//+[{"user":"chofoteddy"},+{"user":"bart"}]
console.log(response);+//+["chofoteddy",+"bart"]|1079430|1079431|AJAX+/+JQuery+(推荐)|1079432|如果您使用JQuery通过AJAX带来信息。我建议您在"dataType“属性中输入"+JSON”值，这样无论您是否获得JSON，JQuery都会为您验证它，并通过它们的函数"success“和"error”使其可知。示例：|1079433|$.ajax({
++++url:+'http://www.something.com',
++++data:+$('#formId').serialize(),
++++method:+'POST',
++++dataType:+'json',
++++//+"sucess"+will+be+executed+only+if+the+response+status+is+200+and+get+a+JSON
++++success:+function+(json)+{},
++++//+"error"+will+run+but+receive+state+200,+but+if+you+miss+the+JSON+syntax
++++error:+function+(xhr)+{}
});|1079434|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|1E|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|1F|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|1G|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|1H|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|1I|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|1J|8|@]|9|@]|A|$]]|$1|N|3|O|5|D|7|1K|8|@]|9|@]|A|$E|F]]|$1|P|3|Q|5|6|7|1L|8|@]|9|@]|A|$]]|$1|R|3|S|5|D|7|1M|8|@]|9|@]|A|$E|F]]|$1|T|3|U|5|6|7|1N|8|@]|9|@]|A|$]]|$1|V|3|W|5|D|7|1O|8|@]|9|@]|A|$E|F]]|$1|X|3|Y|5|6|7|1P|8|@]|9|@]|A|$]]|$1|Z|3|10|5|D|7|1Q|8|@]|9|@]|A|$E|F]]|$1|11|3|12|5|6|7|1R|8|@]|9|@]|A|$]]|$1|13|3|14|5|D|7|1S|8|@]|9|@]|A|$E|F]]|$1|15|3|-4|5|6|7|1T|8|@]|9|@]|A|$]]|$1|16|3|17|5|6|7|1U|8|@]|9|@]|A|$]]|$1|18|3|19|5|6|7|1V|8|@]|9|@]|A|$]]|$1|1A|3|1B|5|D|7|1W|8|@]|9|@]|A|$E|F]]|$1|1C|3|-4|5|6|7|1X|8|@]|9|@]|A|$]]]|1D|$]]

<h3>Solution 3 (fastest way)</h3>

<pre><code>/**
 * @param Object
 * @returns boolean
 */
function isJSON (something) {
 if (typeof something != 'string')
 something = JSON.stringify(something);

 try {
 JSON.parse(something);
 return true;
 } catch (e) {
 return false;
 }
}
</code></pre>

You can use it:

<pre><code>var myJson = [{"user":"chofoteddy"}, {"user":"bart"}];
isJSON(myJson); // true
</code></pre>

<hr />

The best way to validate that an object is of type JSON or array is as follows:

<pre><code>var a = [],
 o = {};
</code></pre>

<h3>Solution 1</h3>

<pre><code>toString.call(o) === '[object Object]'; // true
toString.call(a) === '[object Array]'; // true
</code></pre>

<h3>Solution 2</h3>

<pre><code>a.constructor.name === 'Array'; // true
o.constructor.name === 'Object'; // true
</code></pre>

But, strictly speaking, an array is part of a JSON syntax. Therefore, the following two examples are part of a JSON response:

<pre><code>console.log(response); // {"message": "success"}
console.log(response); // {"user": "bart", "id":3}
</code></pre>

And:

<pre><code>console.log(response); // [{"user":"chofoteddy"}, {"user":"bart"}]
console.log(response); // ["chofoteddy", "bart"]
</code></pre>

<hr />

<h3>AJAX / JQuery (recommended)</h3>

If you use JQuery to bring information via AJAX. I recommend you put in the "dataType" attribute the "json" value, that way if you get a JSON or not, JQuery validate it for you and make it known through their functions "success" and "error". Example:

<pre><code>$.ajax({
 url: 'http://www.something.com',
 data: $('#formId').serialize(),
 method: 'POST',
 dataType: 'json',
 // "sucess" will be executed only if the response status is 200 and get a JSON
 success: function (json) {},
 // "error" will run but receive state 200, but if you miss the JSON syntax
 error: function (xhr) {}
});
</code></pre>

blocks|key|864819|text|var+checkJSON+=+function(m)+{

+++if+(typeof+m+==+'object')+{+
++++++try{+m+=+JSON.stringify(m);+}
++++++catch(err)+{+return+false;+}+}

+++if+(typeof+m+==+'string')+{
++++++try{+m+=+JSON.parse(m);+}
++++++catch+(err)+{+return+false;+}+}

+++if+(typeof+m+!=+'object')+{+return+false;+}
+++return+true;

};


checkJSON(JSON.parse('{}'));++++++//true
checkJSON(JSON.parse('{"a":0}'));+//true
checkJSON('{}');++++++++++++++++++//true
checkJSON('{"a":0}');+++++++++++++//true
checkJSON('x');+++++++++++++++++++//false
checkJSON('');++++++++++++++++++++//false
checkJSON();++++++++++++++++++++++//false|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|864820|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>var checkJSON = function(m) {

 if (typeof m == 'object') { 
 try{ m = JSON.stringify(m); }
 catch(err) { return false; } }

 if (typeof m == 'string') {
 try{ m = JSON.parse(m); }
 catch (err) { return false; } }

 if (typeof m != 'object') { return false; }
 return true;

};


checkJSON(JSON.parse('{}')); //true
checkJSON(JSON.parse('{"a":0}')); //true
checkJSON('{}'); //true
checkJSON('{"a":0}'); //true
checkJSON('x'); //false
checkJSON(''); //false
checkJSON(); //false
</code></pre>

blocks|key|1079506|text|我真的不喜欢公认的答案。首先也是最重要的，它需要jQuery，这并不总是可用的或必需的。其次，它对对象做了一个完全的字符串，这对我来说是夸大其词。下面是一个简单的函数，它只使用lodash库的几个部分来实现泛型，从而彻底检测值是否类似于JSON。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1079507|import+*+as+isNull+from+'lodash/isNull'
import+*+as+isPlainObject+from+'lodash/isPlainObject'
import+*+as+isNumber+from+'lodash/isNumber'
import+*+as+isBoolean+from+'lodash/isBoolean'
import+*+as+isString+from+'lodash/isString'
import+*+as+isArray+from+'lodash/isArray'

function+isJSON(val)+{
++if+(isNull(val)
+++%7C%7C+isBoolean(val)
+++%7C%7C+isString(val))
++++return+true;
++if+(isNumber(val))+
+++++return+!isNaN(val)+&&+isFinite(val)
++if+(isArray(val))
++++return+Array.prototype.every.call(val,+isJSON)
++if+(isPlainObject(val))+{
++++for+(const+key+of+Object.keys(val))+{
++++++if+(!isJSON(val[key]))
++++++++return+false
++++}
++++return+true
++}
++return+false
}|code-block|syntax|javascript|1079508|我甚至花时间把它放在npm中作为一个包：https://npmjs.com/package/is-json-object。将它与诸如Webpack之类的东西一起使用，以将其放入浏览器中。|1079509|希望这对某些人有帮助！|1079510|entityMap|0|LINK|mutability|MUTABLE|url|https://lodash.com/|1|https://npmjs.com/package/is-json-object|2^0|2G|6|0|0|0|K|14|1|1U|7|2|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@$A|Y|B|Z|1|10]]|C|$]]|$1|D|3|E|5|F|7|11|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|12|8|@]|9|@$A|13|B|14|1|15]|$A|16|B|17|1|18]]|C|$]]|$1|K|3|L|5|6|7|19|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|1A|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]|W|$5|P|Q|R|C|$S|T]]]]

I don't really like the accepted answer. First and foremost it requires jQuery, which is not always available or required. Secondly, it does a full stringification of the object which to me is overkill. Here's a simple function that thoroughly detects whether a value is JSON-like, using nothing more than a few parts of the <a href="https://lodash.com/" rel="nofollow noreferrer">lodash</a> library for genericity.



<pre><code>import * as isNull from 'lodash/isNull'
import * as isPlainObject from 'lodash/isPlainObject'
import * as isNumber from 'lodash/isNumber'
import * as isBoolean from 'lodash/isBoolean'
import * as isString from 'lodash/isString'
import * as isArray from 'lodash/isArray'

function isJSON(val) {
 if (isNull(val)
 || isBoolean(val)
 || isString(val))
 return true;
 if (isNumber(val)) 
 return !isNaN(val) &amp;&amp; isFinite(val)
 if (isArray(val))
 return Array.prototype.every.call(val, isJSON)
 if (isPlainObject(val)) {
 for (const key of Object.keys(val)) {
 if (!isJSON(val[key]))
 return false
 }
 return true
 }
 return false
}
</code></pre>

I've even taken the time to put it up in npm as a package: <a href="https://npmjs.com/package/is-json-object" rel="nofollow noreferrer">https://npmjs.com/package/is-json-object</a>. Use it together with something like <a href="https://lodash.com/" rel="nofollow noreferrer">Webpack</a> to get it in the browser.

Hope this helps someone!

blocks|key|1079531|text|我尝试了所有的建议答案，对我来说都不起作用，所以我不得不使用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1079532|jQuery.isEmptyObject()|code-block|syntax|javascript|1079533|帮助别人解决这个问题的hoe|1079534|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

i tried all of the suggested answers, nothing worked for me, so i had to use

<pre><code>jQuery.isEmptyObject()
</code></pre>

hoe that helps someone else out with this issue

My server side code returns a value which is a JSON object on success and a string 'false' on failure. Now how can I check whether the returned value is a JSON object?

How can I check if a value is a JSON object?

服务器

jQuery

JSON

我的服务器端代码成功时返回一个JSON对象的值，失败时返回一个字符串'false‘。现在如何检查返回值是否为JSON对象？

问如何检查值是否为JSON对象？
EN

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