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Safely turning a JSON string into an object
(28 answers)
Closed 7 years ago.
I want to parse a JSON string in JavaScript. The response is something like
var response = '{"result":true,"count":1}';
How can I get the values result and count from this?
The standard way to parse JSON in JavaScript is JSON.parse()
The JSON API was introduced with ES5 (2011) and has since been implemented in >99% of browsers by market share, and Node.js. Its usage is simple:
const json = '{ "fruit": "pineapple", "fingers": 10 }';
const obj = JSON.parse(json);
console.log(obj.fruit, obj.fingers);
The only time you won't be able to use JSON.parse() is if you are programming for an ancient browser, such as IE 7 (2006), IE 6 (2001), Firefox 3 (2008), Safari 3.x (2009), etc. Alternatively, you may be in an esoteric JavaScript environment that doesn't include the standard APIs. In these cases, use json2.js, the reference implementation of JSON written by Douglas Crockford, the inventor of JSON. That library will provide an implementation of JSON.parse().
When processing extremely large JSON files, JSON.parse() may choke because of its synchronous nature and design. To resolve this, the JSON website recommends third-party libraries such as Oboe.js and clarinet, which provide streaming JSON parsing.
jQuery once had a $.parseJSON() function, but it was deprecated with jQuery 3.0. In any case, for a long time, it was nothing more than a wrapper around JSON.parse().
WARNING!
This answer stems from an ancient era of JavaScript programming during which there was no builtin way to parse JSON. The advice given here is no longer applicable and probably dangerous. From a modern perspective, parsing JSON by involving jQuery or calling eval() is nonsense. Unless you need to support IE 7 or Firefox 3.0, the correct way to parse JSON is JSON.parse().
First of all, you have to make sure that the JSON code is valid.
After that, I would recommend using a JavaScript library such as jQuery or Prototype if you can because these things are handled well in those libraries.
On the other hand, if you don't want to use a library and you can vouch for the validity of the JSON object, I would simply wrap the string in an anonymous function and use the eval function.
This is not recommended if you are getting the JSON object from another source that isn't absolutely trusted because the eval function allows for renegade code if you will.
Here is an example of using the eval function:
var strJSON = '{"result":true,"count":1}';
var objJSON = eval("(function(){return " + strJSON + ";})()");
alert(objJSON.result);
alert(objJSON.count);
If you control what browser is being used or you are not worried people with an older browser, you can always use the JSON.parse method.
This is really the ideal solution for the future.
If you are getting this from an outside site it might be helpful to use jQuery's getJSON. If it's a list you can iterate through it with $.each
$.getJSON(url, function (json) {
alert(json.result);
$.each(json.list, function (i, fb) {
alert(fb.result);
});
});
If you want to use JSON 3 for older browsers, you can load it conditionally with:
<script>
window.JSON ||
document.write('<script src="//cdnjs.cloudflare.com/ajax/libs/json3/3.2.4/json3.min.js"><\/scr'+'ipt>');
</script>
Now the standard window.JSON object is available to you no matter what browser a client is running.
The following example will make it clear:
let contactJSON = '{"name":"John Doe","age":"11"}';
let contact = JSON.parse(contactJSON);
console.log(contact.name + ", " + contact.age);
// Output: John Doe, 11
If you pass a string variable (a well-formed JSON string) to JSON.parse from MVC #Viewbag that has doublequote, '"', as quotes, you need to process it before JSON.parse (jsonstring)
var jsonstring = '#ViewBag.jsonstring';
jsonstring = jsonstring.replace(/"/g, '"');
You can either use the eval function as in some other answers. (Don't forget the extra braces.) You will know why when you dig deeper), or simply use the jQuery function parseJSON:
var response = '{"result":true , "count":1}';
var parsedJSON = $.parseJSON(response);
OR
You can use this below code.
var response = '{"result":true , "count":1}';
var jsonObject = JSON.parse(response);
And you can access the fields using jsonObject.result and jsonObject.count.
Update:
If your output is undefined then you need to follow THIS answer. Maybe your json string has an array format. You need to access the json object properties like this
var response = '[{"result":true , "count":1}]'; // <~ Array with [] tag
var jsonObject = JSON.parse(response);
console.log(jsonObject[0].result); //Output true
console.log(jsonObject[0].count); //Output 1
The easiest way using parse() method:
var response = '{"a":true,"b":1}';
var JsonObject= JSON.parse(response);
this is an example of how to get values:
var myResponseResult = JsonObject.a;
var myResponseCount = JsonObject.b;
JSON.parse() converts any JSON String passed into the function, to a JSON object.
For better understanding, press F12 to open the Inspect Element of your browser, and go to the console to write the following commands:
var response = '{"result":true,"count":1}'; // Sample JSON object (string form)
JSON.parse(response); // Converts passed string to a JSON object.
Now run the command:
console.log(JSON.parse(response));
You'll get output as Object {result: true, count: 1}.
In order to use that object, you can assign it to the variable, let's say obj:
var obj = JSON.parse(response);
Now by using obj and the dot(.) operator you can access properties of the JSON Object.
Try to run the command
console.log(obj.result);
Without using a library you can use eval - the only time you should use. It's safer to use a library though.
eg...
var response = '{"result":true , "count":1}';
var parsedJSON = eval('('+response+')');
var result=parsedJSON.result;
var count=parsedJSON.count;
alert('result:'+result+' count:'+count);
If you like
var response = '{"result":true,"count":1}';
var JsonObject= JSON.parse(response);
you can access the JSON elements by JsonObject with (.) dot:
JsonObject.result;
JsonObject.count;
I thought JSON.parse(myObject) would work. But depending on the browsers, it might be worth using eval('('+myObject+')'). The only issue I can recommend watching out for is the multi-level list in JSON.
An easy way to do it:
var data = '{"result":true,"count":1}';
var json = eval("[" +data+ "]")[0]; // ;)
If you use Dojo Toolkit:
require(["dojo/json"], function(JSON){
JSON.parse('{"hello":"world"}', true);
});
As mentioned by numerous others, most browsers support JSON.parse and JSON.stringify.
Now, I'd also like to add that if you are using AngularJS (which I highly recommend), then it also provides the functionality that you require:
var myJson = '{"result": true, "count": 1}';
var obj = angular.fromJson(myJson);//equivalent to JSON.parse(myJson)
var backToJson = angular.toJson(obj);//equivalent to JSON.stringify(obj)
I just wanted to add the stuff about AngularJS to provide another option. NOTE that AngularJS doesn't officially support Internet Explorer 8 (and older versions, for that matter), though through experience most of the stuff seems to work pretty well.
If you use jQuery, it is simple:
var response = '{"result":true,"count":1}';
var obj = $.parseJSON(response);
alert(obj.result); //true
alert(obj.count); //1
I’m quite new to postman (and coding) and was trying to find and piece together many snippets of scripts to make it work the way I want.
What I want is very simple: I have a list of IDs that I want to make a POST in each of them, get one of the responseBody as a variable and do another POST. I think I’m close but I can’t manage to get it to work.
I’ve tried:
Two POST request in the same Collection and running the collection.
In the first request I have a POST to
https://APIADDRESS/?order_id{{orderid}}&contract[copy_order_data]=true
On the Pre-request Script tab:
var orderids = pm.environment.get(“orderids”);
if (!orderids) {
orderids = [“bc46bf79-2846-44ed-ac4d-78c77c92ccc8”,“81aacc33-1ade-41a3-b23e-06b03b526b8f”];
}
var currentOrderId = orderids.shift();
pm.environment.set(“orderid”, currentOrderId);
pm.environment.set(“orderids”, orderids);
On the Tests tab:
var orderids = pm.environment.get(“orderids”);
if (orderids && orderids.length > 0) {
var jsonData = JSON.parse(responseBody);
postman.setEnvironmentVariable(“invoice.id”, jsonData.invoice.id);
postman.setNextRequest(“Create invoice”);
} else {
postman.setNextRequest(null);
}
invoice.id is a environment variable populated with the response body of the first action/post and then using the variable on the second action/post.
And then the second request would be a POST to
https://APIADDRESS/invoices/{{invoice.id}}/finalize.json
Of course this doesn’t work. Either it doesn't run the second request in the collection or it doesn't do the loope to more than 1 ID on the list.
So I thought that putting the second POST inside the first one would solve it. But I had no luck.
Can please someone help me?
I have tried mentioned use case with sample API's provided by POSTMAN.
Can you try it?
First POST Method Request : https://postman-echo.com/post
Pre-request Script of first POST method
var orderids = pm.environment.get("orderids");
if(!orderids ){
orderids = ["bc46bf79-2846-44ed-ac4d-78c77c92ccc8","81aacc33-1ade-41a3-b23e-06b03b526b8f"];
}
var currentOrderId = orderids.shift();
pm.environment.set("orderid", currentOrderId);
pm.environment.set("orderids", orderids);
Tests Tab of first POST Method
var orderids = pm.environment.get("orderids");
if (orderids && orderids.length > 0) {
var jsonData = JSON.parse(responseBody);
postman.setEnvironmentVariable("invoice.id", jsonData.headers.host);
postman.setNextRequest("Test1");
} else {
postman.setNextRequest(null);
}
Second POST Method Reqeust: https://postman-echo.com/post?key={{invoice.id}}
After executing the above collection it will set orederids and invoice.id value in environment variables and then it will call next POST Method.
Hope this will help you.
Thanks #HalfBloodPrince, from the Postman Echo it worked but in my case it doesn't :S
What I manage to get it working was using a Json file as a list of Orderids.
In that case I've separated all requests.
Request1 - https://APIADDRESS/?order_id{{orderid}}&contract[copy_order_data]=true
Tests tab:
var jsonData = JSON.parse(responseBody);
postman.setEnvironmentVariable("invoice.id", jsonData.invoice.id);
Request2 - https://APIADDRESS/invoices/{{invoice.id}}/finalize.json
That way everything is in a neat and organized way.
Thanks
After posting the request, API return response body as string
Response body look like
{ UniqueID = 93243434,birthGender = M,birthDate = 11/1/2018 5:51:18
PM, familyNames = James, givenNames = Test }
when I try to set the environment variable using the below code
var data = JSON.parse(responseBody);
postman.setEnvironmentVariable("currentUniqueId", data.UniqueId);
I got the below error on test results
Error message:
There was an error in evaluating the test script: JSONError:
Unexpected token 'U' at 1:3 { UniqueID = 93243434,birthGender =
M,birthDate = 11/1/2018 5:51:18 PM, family ^
my goal is I need to extract the value 93243434 and assign to environment variable.
Hi you are using the correct way but you can try this version
var jsonData = pm.response.json();
pm.environment.set("UNIQUE_ID", jsonData.UniqueID);
The set("UNIQUE_ID" will help you save it in variable and you can name it as you want and jsonData.uniqueID will extract what you want to get from the Json response
If you view my approach I am extracting Access code and company id and saving it in variable and calling it in all next api's
You are using a notation pattern that is deprecated.
Instead of set your variable using:
var data = JSON.parse(responseBody);
postman.setEnvironmentVariable("currentUniqueId", data.UniqueId);
Try to set your variable this way:
pm.environment.set('currentUniqueId', pm.response.json().UniqueID);
To get more information, try: https://learning.getpostman.com/docs/postman/scripts/test_examples/
Using a GET in postman with the URL posted below, I am able to store the entire response header in question with all of its data in a var, the issue for me is how do I verify the pieces of data inside that var
here is my URL
http://localhost/v1/accounts?pageNumber=1&pageSize=2
[
using postman I am able to get the above in a var
var XPaginationData = postman.getResponseHeader(pm.globals.get("PaginationHeader"));
pm.globals.set("XPaginationData", XPaginationData);
is there a way to get the individual values inside the response header X-Pagination stored in a different var to assert later
using this in postman
pm.globals.set("XPaginationData", JSON.stringify(pm.response.headers));
console.log(JSON.parse(pm.globals.get('XPaginationData')));
console.log(JSON.parse(pm.globals.get('XPaginationData'))[4].value);
I get
how would i go about getting "TotalCount" for example
BIG EDIT:
thanks to a coworker, the solution is this
//Filtering Response Headers to get PaginationHeader
var filteredHeaders = pm.response.headers.all()
.filter(headerObj => {
return headerObj.key == pm.globals.get("PaginationHeader");
});
// JSON parse the string of the requested response header
// from var filteredHeaders
var paginationObj = filteredHeaders[0].value;
paginationObj = JSON.parse(paginationObj);
//Stores global variable for nextpageURL
var nextPageURL = paginationObj.NextPageLink;
postman.setGlobalVariable("nextPageURL", nextPageURL);
You could use JSON.stringfy() when saving the environment variable and then use JSON.parse() to access the different properties or property that you need.
If you set a global variable for the response headers like this:
pm.globals.set('PaginationHeader', JSON.stringify(pm.response.headers))
Then you can get any of the data from the variable like this:
console.log(JSON.parse(pm.globals.get('PaginationHeader'))[1].value)
The image shows how this works in Postman. The ordering of the headers returned in the console is inconsistent so you will need to find the correct one to extract data from the X-Pagination header
Looks like an issue with Postman itself.
The only solution that worked for me was to stringify & parse the JSON again, like this:
var response = JSON.parse(JSON.stringify(res))
After doing this, the headers and all other properties are accessible as expected.
I have an environment variable called "url", the value is a combination of several other variables in the same environment.
Here is the bulk environment variable definition:
scheme:http
server:localhost
port::55881
application:/
url:{{scheme}}://{{server}}{{port}}{{application}}
As you can see, url contains other variables.
This works great in the actual request (I'm using {{url}} when addressing my service), but when I try to use the same variable in my scripted tests (In the Tests tab), I'm getting the un-evaluated version.
var serviceUrl = pm.variables.get("url");
console.log(serviceUrl); //Yields {{scheme}}://{{server}}{{port}}{{application}}
Is there a way to get the evaluated value inside my tests?
Thanks!
Complete test for more insight:
var jsonData = JSON.parse(responseBody);
tests["Status code is 200"] = responseCode.code === 200;
var ordrereferanse = jsonData.Ordrereferanse;
tests.OrdreReferanse = ordrereferanse.length > 0;
//Have to do this
var scheme = pm.variables.get("scheme");
var server = pm.variables.get("server");
var port = pm.variables.get("port");
var application = pm.variables.get("application");
var api_key = pm.variables.get("api_key");
var serviceUrl = scheme + "://" + server + port + application;
//Instead of this - an environment variable defined like this "{{scheme}}://{{server}}{{port}}{{application}}"
//var serviceUrl = pm.variables.get("url");
//remaining test - go to url to verify that the resource is created and the order reference is set
var infoUrl = serviceUrl + "ordreinformasjon/" + ordrereferanse + "?format=json&api_key=" + api_key;
pm.sendRequest(infoUrl, function (err, response) {
var info = response.json();
console.log(info);
tests.OrdreInformasjonOrdreReferanse = info.OrdreReferanse === ordrereferanse;
});
This would work but I'm not sure what you're trying to achieve:
var scheme = pm.variables.get("scheme")
var server = pm.variables.get("server")
var port = pm.variables.get("port")
var application = pm.variables.get("application")
console.log(`${scheme}://${server}${port}${application}`)
That would log out http://localhost:55881/ to the console.
The {{...}} syntax doesn't work in the way that you had it in the environment file. As it's just storing everything as a string so that's why you would get that output.
You could use {{scheme}}://{{server}}{{port}}{{application}} as the URL but not in the tests using the same syntax.
UPDATE
After seeing the update to the question - Could you not combine the separate variables into a single url variable and construct the infoUrl variable in the following way:
var infoUrl = `${pm.variables.get("url")}ordreinformasjon/${ordrereferanse}?format=json&api_key=${pm.variables.get("api_key")}`
Then use a different environment file with the same url key but with a different value if you need to point the request at a staging or production URL.
I've also noticed that you're using the older tests syntax rather than the newer pm.test() syntax, that might clean up some of the code for you.