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Express.js res.json() Function
  • Last Updated : 05 May, 2021

The res.json() function sends a JSON response. This method sends a response (with the correct content-type) that is the parameter converted to a JSON string using the JSON.stringify() method.
Syntax: 
 

res.json( [body] )

Parameters: The body parameter is the body which is to be sent in the response.
Return Value: It returns an Object.
Installation of express module: 
 

1. You can visit the link to Install express module. You can install this package by using this command. 
 

npm install express

2. After installing the express module, you can check your express version in command prompt using the command. 
 

npm version express

3. After that, you can just create a folder and add a file for example, index.js. To run this file you need to run the following command. 
 



node index.js

Example 1: Filename: index.js 
 

javascript




var express = require('express');
var app = express();
var PORT = 3000;
 
// Without middleware
app.get('/', function(req, res){
    res.json({ user: 'geek' });
});
 
app.listen(PORT, function(err){
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

Steps to run the program: 
 

1. The project structure will look like this: 
 

2. Make sure you have installed express module using the following command: 
 

npm install express

3. Run index.js file using below command: 
 

node index.js

Output: 
 



Server listening on PORT 3000

4. Now open browser and go to http://localhost:3000/, now on your screen you will see the following output: 
 

{"user":"geek"}

 

Example 2: Filename: index.js 
 

javascript




var express = require('express');
var app = express();
var PORT = 3000;
 
// With middleware
app.use('/', function(req, res, next){
    res.json({title: "GeeksforGeeks"})
    next();
})
 
app.get('/', function(req, res){
     console.log("User Page")
     res.end();
});
 
app.listen(PORT, function(err){
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

Run index.js file using below command: 
 

node index.js

Now open a browser and go to http://localhost:3000/, now on your screen you will see the following output: 
 

{"title":"GeeksforGeeks"}

And you will see the following output on your console: 
 

User Page

Reference: https://expressjs.com/en/4x/api.html#res.json
 

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