# node.js – Proper way to return JSON using node or Express

## The Question :

478 people think this question is useful

So, one can attempt to fetch the following JSON object:

$curl -i -X GET http://echo.jsontest.com/key/value/anotherKey/anotherValue HTTP/1.1 200 OK Access-Control-Allow-Origin: * Content-Type: application/json; charset=ISO-8859-1 Date: Wed, 30 Oct 2013 22:19:10 GMT Server: Google Frontend Cache-Control: private Alternate-Protocol: 80:quic,80:quic Transfer-Encoding: chunked { "anotherKey": "anotherValue", "key": "value" }$



Is there a way to produce exactly the same body in a response from a server using node or express? Clearly, one can set the headers and indicate that the content-type of the response is going to be “application/json”, but then there are different ways to write/send the object. The one that I have seen commonly being used is by using a command of the form:

response.write(JSON.stringify(anObject));



However, this has two points where one could argue as if they were “problems”:

• We are sending a string.
• Moreover, there is no new line character in the end.

Another idea is to use the command:

response.send(anObject);



This appears to be sending a JSON object based on the output of curl similar to the first example above. However, there is no new line character in the end of the body when curl is again being used on a terminal. So, how can one actually write down something like this with a new line character appended in the end using node or node/express?

664 people think this answer is useful

That response is a string too, if you want to send the response prettified, for some awkward reason, you could use something like JSON.stringify(anObject, null, 3)

It’s important that you set the Content-Type header to application/json, too.

var http = require('http');

var app = http.createServer(function(req,res){
res.end(JSON.stringify({ a: 1 }));
});
app.listen(3000);

// > {"a":1}



Prettified:

var http = require('http');

var app = http.createServer(function(req,res){
res.end(JSON.stringify({ a: 1 }, null, 3));
});
app.listen(3000);

// >  {
// >     "a": 1
// >  }



I’m not exactly sure why you want to terminate it with a newline, but you could just do JSON.stringify(...) + '\n' to achieve that.

# Express

In express you can do this by changing the options instead.

'json replacer' JSON replacer callback, null by default

'json spaces' JSON response spaces for formatting, defaults to 2 in development, 0 in production

Not actually recommended to set to 40

app.set('json spaces', 40);



Then you could just respond with some json.

res.json({ a: 1 });



It’ll use the 'json spaces‘ configuration to prettify it.

424 people think this answer is useful

Since Express.js 3x the response object has a json() method which sets all the headers correctly for you and returns the response in JSON format.

Example:

res.json({"foo": "bar"});



19 people think this answer is useful

If you are trying to send a json file you can use streams

var usersFilePath = path.join(__dirname, 'users.min.json');

apiRouter.get('/users', function(req, res){
});



13 people think this answer is useful

The res.json() function should be sufficient for most cases.

app.get('/', (req, res) => res.json({ answer: 42 }));



The res.json() function converts the parameter you pass to JSON using JSON.stringify() and sets the Content-Type header to application/json; charset=utf-8 so HTTP clients know to automatically parse the response.

6 people think this answer is useful

If you’re using Express, you can use this:

res.setHeader('Content-Type', 'application/json');
res.send(JSON.stringify({key:"value"}));



or just this

res.json({key:"value"});