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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 The advice given here is no longer applicable and probably dangerous.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!
I'm trying to use a pre-request script to build out a request object based on data pulled from a CSV file. The problem is that the request seems to be set in stone prior to the pre-request script being run. That would seem to make this a mid-request script almost rather than a pre-request.
My code is as follows:
if(ipList === undefined) ipList = "1.2.3.4,2.3.4.5,123.234.345.465";
let ips = ipList.split(',');
let queryArray = [];
for( i=0; i<ips.length; i++){
queryArray.push({ "key": "ip", "value": ips[i] });
}
console.log(queryArray);
pm.request.url.query = queryArray;
console.log(pm.request);
When I hardcode a url query variable in the request to equal 4.3.2.1, the pm.response.url object like this:
pm.request.url.query[0] = {key:"ip", value:"4.3.2.1"}
Note that the url.query[0] part of the object matches the parameter in the actual get request.
When I change the value of pm.request.url.query to equal the new query array, however as you can see here, the query array is set correctly, but the parameters are not appended to the request URL.
So unless I'm doing something wrong, it appears that the request is immutable even to the pre-request scripts.
So my question is this:
Is there a way to modify the url params of a request prior to making the request?
BTW: I know that is might seem odd to have multiple params with the same key in a query, but that's the way this API works and hard coding multiple ip addresses in the query works just fine.
You could just assign a new value to pm.request.url.
Here I had some query params already in the URL, which I had to edit:
const urlSplit = request.url.split('?');
const paramsString = urlSplit[1]; // the second part actually represents the query string we need to modify
const eachParamArray = paramsString.split('&');
let params = {};
eachParamArray.forEach((param) => {
const key = param.split('=')[0];
const value = param.split('=')[1];
Object.assign(params, {[key]: value});
});
params.bla = params.bla + 'foobar';
newQueryString = Object.keys(params).map(key => key + '=' + params[key]).join('&');
pm.request.url = urlSplit[0] + '?' + newQueryString;
In the end, I just constructed a new URL, using the first part of the previous one & the query string with the edited bla parameter.
This seemed to work for me--it didn't change what the UI shows the query string is, but it changed what the actual request was (looking at the console log)
pm.request.url.addQueryParams(["a=1", "b=2"])
pm.request.url.query.remove("b")
I have some parameters called "script_loginAs" etc... named such that people on my team know the parameter is evaluated and not sent.
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 am having an issue with a growing list. Previously I had a normal list, but as it is limited to displaying 100 items, I need to now change this to a growing list, which works fine now and I can get over 100 items loaded when I've put the growing="true" growingThreshold="50" growingScrollToLoad="false" properties on the list.
But now I have an issue with one of the number inputs in the custom list, when entering a number it is not staying set (it has a liveChange event that updates a text component).
I've set a breakpoint in the controller to test and it seems to bug out when I am trying to set the data changes (red arrow on attached image).
Can anyone see the issue with the logic? If any additional code snippets are required I could provide them.
onReceivedQuantityChange: function (oEvent) {
// get model and data
var oModel = this.getOrderModel();
var oData = oModel.getData();
// get item from path
var oItem = this._getOrderItemByPath(oEvent.getSource().getBindingContext(this.MODEL_ORDERS).getPath());
// set received value
oItem._ReceivedValue = oEvent.getParameters().newValue * (oItem.ValuationPrice / oItem.Quantity);
// apply data changes
oModel.setData(oData);
},
Controller code image
onReceivedQuantityChange: function (oEvent) {
var oModel = this.getOrderModel()
var sItemPath = oEvent.getSource().getBindingContext(this.MODEL_ORDERS).getPath()
var iValuationPrice = oModel.getProperty(sItemPath + '/ValuationPrice')
var iQuantity = oModel.getProperty(sItemPath + '/Quantity')
var iNewValue = oEvent.getParameters().newValue
var iReceivedValue = iNewValue * (iValuationPrice / iQuantity)
oModel.setProperty(sItemPath + '/_ReceivedValue', iReceivedValue)
}
If you use setProperty() on the Model you're only chaning the specific Property in DataModel and Sapui5 is able to proceed bindingchanges on this Property only (and not the whole model).
If you get the data out of the model by getData() you are only getting a reference to this Object. If you change something on this Object, you don't have to set it back by setData() (it is already there because you used the reference of this Object).
But Sapui5 need to know that there was a specific change in datamodel and this is done by using setProperty()