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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 The advice given here is no longer applicable and probably dangerous.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
Well i'm a student , and i'm still learning the dart language and the flutter framework, I was trying to make an application that makes you able to login into a site with a http post request and get data by manipulating the response of the html source code with some regular expressions to get what you need from the website,
(something like data scraping)
I tried to do that but nothing worked as planned.
I did this project! years ago and it was for desktop, with vb.net, I used a library called xNet which helped me to do that.
For this case I used the http dart package.
Is this kind of work can be done with dart?
Is there any specific packages for this?
Is there any docs available ?
I know html is not a regular language, i asked if it is possible to use http requests to login into a site!?
if i can do that i can manipulate the response and get what i need with some regular expressions.
I wanna do something like
C#
using (HttpRequest req = new HttpRequest())
{
req.UserAgent = Http.ChromeUserAgent;
req.Cookies = new CookieDictionary(false);
req.Proxy = null;
req.IgnoreProtocolErrors = true;
req.AddParam("login", cin.Text);
req.AddParam("no_anti_inject_password", pass.Text);
try {
string Respo = req.Post("http://www.example.com/login.php").ToString;
// to with that 'Respo'
if (Respo.Contains("disconnect"))
{
//Logged
//example
Match NAME = Regex.Match(Respo, "(.*?)");
name.Text = "Name: " + NAME.Groups(1).Value;
}else{
//not logged
//some code...
}
catch{
//some exception
}
}
HTML is not a regular language and so a regular expression is not a good way to scrape data from html. You may be interested in package:html which implements an HTML parser.
I tried to query Loopback js Model using "inq" (mongo $in) syntax
like this:
let itemNames = [/test/i, /test2/i];
app.models.skill.find({where: {name: {inq: itemNames}}}, ....
But loopback is changing regexp to strings.
loopback sends strings like
{ name: { $in: [ "/test/i", "/test2/i" ] } }
expected to work like described here:
https://docs.mongodb.com/manual/reference/operator/query/in/#use-the-in-operator-with-a-regular-expression
Can you suggest a fix or a workaround for this (but I can't patch loopback itself it is a business requirement)
Loopback accepted my changes,
https://github.com/strongloop/loopback-datasource-juggler/pull/1279
so it should be possible to use regexps like in mongo.
You may create inq item like this:
let itemNames = [new RegExp('/test/i'), new RegExp('/test2/i')];
It worked for me.
I'm trying to implement a searching feature in a Meteor application that re-subscribes/publishes a collection on every search, so there is only the exact Collection necessary in the client. I'm creating a reactive variable searchString, then changing it to the text in the search box on every search, then splitting the string into tags:
// Client
var searchString = "";
var searchStringDep = new Deps.Dependency;
var getSearchString = function(){
searchStringDep.depend();
return searchString;
}
var handle = Deps.autorun(function(){
var tags = getSearchString().split(" ");
tags = _.map(tags, function(tag){
return tag.replace(/[^\w]/g, "");
}).filter(function(t){
return t.toLowerCase();
});
Meteor.subscribe('results', tags);
});
Template.library.events({
'submit form': function(ev){
ev.preventDefault();
searchString = ev.target.search.value;
searchStringDep.changed();
}
})
Then, publishing a new Collection on the server, based on the tags:
// Server
Meteor.publish('results', function(tags){
regTags = _.map(tags, function(tag) { return new RegExp(tag)});
return Samples.find({tags: {$in: regTags}})
});
So I'm trying to match on regexes, but am having a weird issue where the subscription only changes when I add another tag, but changing existing tags fails.
So if the first searchString was tag1 and the second tag1 tag2, it works fine.
But if the first is tag1 and the second is tag2, the Collection doesn't update.
Any help is appreciated...I'm a beginner to Meteor, so if there is a better way to do what I'm trying to do, all suggestions are welcome. Thanks so much
'change #search': function(){
Meteor.subscribe('sampleResults', $('#search').val()); // or if you want on submit it's the same idea
}
and publish like
Meteor.publish('sampleResults, function(text){
return Samples.find({tags: {$regex: text}});
}
A few things:
1) Meteor has a very nice way of setting up reactive variables with the ReactiveVar component. I would suggest using that rather than creating another dependency for a variable.
2) The name that you are subscribing to: results is different than what is published on the server sampleResults and that can cause issues.
3) If you are on Meteor >= 0.9.1 you should be using Tracker and not Deps. You can use Deps if you want, but the new updated API is Tracker and is probably more stable. See the changelog for more details on that.
4) You don't have to set your Deps.autorun function equal to a variable. So you can have it as:
Tracker.autorun(function() {
// Code here
});