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Express.js res.set() Function
  • Last Updated : 07 Jul, 2020

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 retuns a 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




var express = require('express');
var app = express();
var PORT = 3000;
  
// Without middlware
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:

  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 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




var express = require('express');
var app = express();
var PORT = 3000;
  
// With middlware
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);
});

Run index.js file using below command:

node index.js

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

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

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

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