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 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;

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:

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 make a GET request to http://localhost:3000/ with 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

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

Run index.js file using below command:

node index.js

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

Server listening on PORT 3000
gzip
false

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