Express res.json() Function

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 that is to be sent in the response.

Return Value: It returns an Object.

Steps to Install the Express Module:

Step 1: You can install this package by using this command.

npm install express

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

npm version express

Project Structure:

The updated dependencies in package.json file will look like:

"dependencies": {
    "express": "^4.18.2",
}

Example 1: Below is the code of res.json() Function implementation.

const express = require('express');
const app = express();
const 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:

Run the index.js file using the below command: 

node index.js

Console Output: 

Server listening on PORT 3000

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

{"user":"geek"}

Example 2: Below is the code of res.json() Function implementation.

const express = require('express');
const app = express();
const 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);
});

Steps to run the program: 

Run the index.js file using the below command: 

node index.js

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

{"title":"GeeksforGeeks"}

Console Output: And you will see the following output on your console: 

User Page