Express.js req.acceptsEncodings() Function

The req.acceptsEncodings() function returns the first accepted encoding of the specified encodings on the basis of the request Accept-Encoding HTTP header field and it returns false if none of the specified encodings is accepted. 

Syntax:

req.acceptsEncodings(encoding [, ...])

Parameters: The encoding parameter is the specified encoding like ‘compress’, etc. 

Return Value: String (if true) or False.

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

javascript

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

app.get('/', function (req, res) {
    console.log(req.get('Accept-Encoding'));
    console.log(req.acceptsEncodings('gzip'));
    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 make a GET request to http://localhost:3000/ with the header set to ‘Accept-Encoding: gzip’, then you will see the following output on your console:

Server listening on PORT 3000
gzip
gzip

Example 2: Filename: index.js

javascript

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

app.get('/', function (req, res) {
    console.log(req.get('Accept-Encoding'));
    console.log(req.acceptsEncodings('compress'));
    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

Now make a GET request to http://localhost:3000/ with the header set to ‘Accept-Encoding: gzip’, then you will see the following output on your console:

Output:

Server listening on PORT 3000
gzip
false

Reference: https://expressjs.com/en/4x/api.html#req.acceptsEncodings