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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 The advice given here is no longer applicable and probably dangerous.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
So I have a set of results in Postman from a runner on a collection using some data file for iterations - I have the stored data from the runner in the Postman app on Linux, but I want to know how I can get hold of the data. There seems to be a database hidden away in the ~/.config directory (/Desktop/file__0.indexeddb.leveldb) - that looks like it has the data from the results there.
Is there anyway that I can get hold of the raw data - I want to be able to save the results from the database and not faff around with running newman or hacking a server to post the results and then save, I already have 20000 results in a collection. I want to be able to get the responseData from each post and save it to a file - I will not execute the posts again, I need to just work out a way
I've tried KeyLord, FastNoSQL (this crashes), levelDBViewer(Jar), but not having any luck here.
Any suggestions?
inline 25024 of runner.js a simple yet hack for small numbers of results I can do the following
RunnerResultsRequestListItem = __WEBPACK_IMPORTED_MODULE_2_pure_render_decorator___default()(_class = class RunnerResultsRequestListItem extends __WEBPACK_IMPORTED_MODULE_0_react__["Component"] {
constructor(props) {
super(props);
var text = props.request.response.body,
blob = new Blob([text], { type: 'text/plain' }),
anchor = document.createElement('a');
anchor.download = props.request.ref + ".txt";
anchor.href = (window.webkitURL || window.URL).createObjectURL(blob);
anchor.dataset.downloadurl = ['text/plain', anchor.download, anchor.href].join(':');
anchor.click();
it allows me to save but obviously I have to click save for now, anyone know how to automate the saving part - please add something here!
Im currently trying to get used to POSTMAN and i was wondering if there is a way to store variables from my request JSON Body via Pre Request in some environment variable so ican resuse it in the tests for response value cheks
This is how my json File might look like
{
"text" : "myText",
"attachments": {
"text": "myText2",
"anotherText" : "myText3"
}
So i want to get all Values, store them in a variable before sending my request, and then test if they match the expected value in my response
(example: myText2 gets mapped to green, myText3 gets mapped to red and so on)
That would make it possible to write one test for several request
Thanks a lot!
You can write the following in your script:
let body = JSON.parse(pm.request.body);
_.forEach(body, (value, key) => pm.environment.set(key, JSON.stringify(value)));
This will set each key and it's associated value as an environment variables.
Note you'll need to JSON.parse the value in the test script before using it for testing.
For eg in your test script you'll need to do something like this:
let attachments = JSON.parse(pm.environment.get('attachments'));
pm.test('All attachments are of correct value', function () {
// ...write your test here using the `attachments` variable
});
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
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.