How to create JSON string in JavaScript?

Question

window.onload = function(){
    var obj = '{
            "name" : "Raj",
            "age"  : 32,
            "married" : false
            }';

    var val = eval('(' + obj + ')');
    alert( "name : " + val.name + "\n" +
           "age  : " + val.age  + "\n" +
           "married : " + val.married );

}

In a code something like this, I am trying to create JSON string just to play around. It's throwing error, but if I put all the name, age, married in one single line (line 2) it doesn't. Whats the problem?

See this answers stackoverflow.com/questions/3904269/…

powtac
– powtac

2012-01-22 19:00:40 +00:00
Commented Jan 22, 2012 at 19:00 — powtac
– powtac, Commented Jan 22, 2012 at 19:00

Akhil Sekharan · Accepted Answer · 2012-11-21 08:20:48Z

330

The way i do it is:

   var obj = new Object();
   obj.name = "Raj";
   obj.age  = 32;
   obj.married = false;
   var jsonString= JSON.stringify(obj);

I guess this way can reduce chances for errors.

answered Nov 21, 2012 at 8:20

Akhil Sekharan

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1 Comment

s6mike Over a year ago

I think var obj = { name: 'Raj', age: 32, etc} is better.

bardiir · Accepted Answer · 2021-04-08 17:21:00Z

97

Disclaimer: This is not an answer to follow for the best way how to create JSON in JavaScript itself. This answer mostly tackles the question of "what is the problem?" or WHY the code above does not work - which is a wrong string concatenation attempt in JavaScript and does not tackle why String concatenation is a very bad way of creating a JSON String in the first place.

See here for best way to create JSON: https://stackoverflow.com/a/13488998/1127761

Read this answer to understand why the code sample above does not work.

Javascript doesn't handle Strings over multiple lines.

You will need to concatenate those:

var obj = '{'
       +'"name" : "Raj",'
       +'"age"  : 32,'
       +'"married" : false'
       +'}';

You can also use template literals in ES6 and above: (See here for the documentation)

var obj = `{
           "name" : "Raj",
           "age" : 32,
           "married" : false,
           }`;

edited Apr 8, 2021 at 17:21

answered Jan 22, 2012 at 19:00

bardiir

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8 Comments

Phrogz Over a year ago

Or put a \ at the end of each line in the literal.

Blue Over a year ago

For multi-line strings, instead of single or double quotes, you can use ` (back-tick character. to the left of the #1 key). These are called 'template literals'.

AsTeR Over a year ago

Definitely: don't settle for this answer and look to the others.

bardiir Over a year ago

Template literals are ECMA Script 2015 Standard. This question and answer is from 2012 already. But I'll edit it in :)

rory.ap Over a year ago

Really? String concatenation from scratch is the best way to build JSON? I think the other answer should be the accepted answer.

|

Didier Ghys · Accepted Answer · 2012-01-22 19:05:25Z

67

The function JSON.stringify will turn your json object into a string:

var jsonAsString = JSON.stringify(obj);

In case the browser does not implement it (IE6/IE7), use the JSON2.js script. It's safe as it uses the native implementation if it exists.

answered Jan 22, 2012 at 19:05

Didier Ghys

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Comments

Hidden · Accepted Answer · 2017-04-19 07:18:44Z

37

This can be pretty easy and simple

var obj = new Object();
obj.name = "Raj";
obj.age = 32;
obj.married = false;

//convert object to json string
var string = JSON.stringify(obj);

//convert string to Json Object
console.log(JSON.parse(string)); // this is your requirement.

answered Apr 19, 2017 at 7:18

Hidden

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Comments

TimWolla · Accepted Answer · 2012-01-22 18:58:48Z

18

Use JSON.stringify:

> JSON.stringify({ asd: 'bla' });
'{"asd":"bla"}'

answered Jan 22, 2012 at 18:58

TimWolla

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4 Comments

Douglas Over a year ago

See also json2.js if you need to support older browsers.

Douglas Over a year ago

Yes, here's a link to his GitHub project list: github.com/douglascrockford

TimWolla Over a year ago

@nepsdotin Douglas at SO is not Douglas Crockford, "to his GitHub"

Douglas Over a year ago

Aah, missed that, nope, I'm not Crockford!

SULFIKAR A N · Accepted Answer · 2014-01-06 05:14:52Z

8

I think this way helps you...

var name=[];
var age=[];
name.push('sulfikar');
age.push('24');
var ent={};
for(var i=0;i<name.length;i++)
{
ent.name=name[i];
ent.age=age[i];
}
JSON.Stringify(ent);

answered Jan 6, 2014 at 5:14

SULFIKAR A N

4464 silver badges13 bronze badges

Comments

Mike · Accepted Answer · 2023-05-12 11:53:44Z

0

The Answer from @Akhil is still the best for me. one user asked how to do nested properties, and I wanted to expand the solution like this:

var obj = new Object();
var nameobj = new Object();
nameobj.firstname = "Raj";
nameobj.lastname = "whatever";
obj.name = nameobj;
obj.age  = 32;
obj.married = false;
var jsonString= JSON.stringify(obj);

answered May 12, 2023 at 11:53

Mike

35 bronze badges

Comments

Marc B · Accepted Answer · 2012-01-22 19:00:10Z

-6

json strings can't have line breaks in them. You'd have to make it all one line: {"key":"val","key2":"val2",etc....}.

But don't generate JSON strings yourself. There's plenty of libraries that do it for you, the biggest of which is jquery.

answered Jan 22, 2012 at 19:00

Marc B

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4 Comments

user1106925 Over a year ago

JSON can have line breaks, but JavaScript string literal syntax cannot.

Marc B Over a year ago

interally within a string, yeah, but not between key/value pairs.

user1106925 Over a year ago

I think you're confusing JavaScript string literal syntax which cannot contain an unescaped newline character, and JSON markup. JSON markup can most certainly contain line breaks.

user1106925 Over a year ago

...paste the code in your question into jsonlint.com (without the etc.... of course). After clicking Validate, you'll see that it actually inserts newlines when it pretty-prints.

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