Express.js res.set() Function

The res.set() function is used to set the response HTTP header field to value. To set multiple fields at once, pass an object as the parameter.

Syntax: 

res.set(field [, value])

Parameters: The field parameter is the name of the field and the value parameter is the value assigned to the field parameter.

Return Value: It returns an Object.

Installation of the express module: 

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

npm install express

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

npm version express

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

Project Structure:

Example 1: Filename: index.js 

const express = require('express');
const app = express();
const PORT = 3000;

// Without middleware
app.get('/', function (req, res) {

    // Setting the response
    res.set({
        'Content-Type': 'application/json'
    });

    // "application/json"
    console.log(res.get('Content-Type'));
    res.end();
});

app.listen(PORT, function (err) {
    if (err) console.log(err);
    console.log("Server listening on PORT", PORT);
});

Steps to run the program: 

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

npm install express

Run the index.js file using the below command: 

node index.js

Output: 

Console Output:

Server listening on PORT 3000

Browser Output:

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

Server listening on PORT 3000
application/json; charset=utf-8

Example 2: Filename: index.js 

const express = require('express');
const app = express();
const PORT = 3000;

// With middleware
app.use('/', function (req, res, next) {
    res.set({
        'Content-Type': 'application/xml'
    });

    next();
})

// Using middleware
app.get('/', function (req, res) {

    console.log(res.get('Content-Type'));
    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

Output:

Console Output:

Server listening on PORT 3000

Browser Output:

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

application/xml; charset=utf-8

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

gouravhammad

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Article Tags :

• Express.js
• JavaScript
• Node.js
• Web Technologies