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Express.js req.is() Function

  • Last Updated : 09 Jul, 2020

The req.is() function returns the matching content-type if the incoming request’s ‘Content-Type’ HTTP header field matches with the MIME type that has been specified by the type parameter and it returns null if the request has no body otherwise it returns false.

Syntax:

req.is( type )

Parameter: The type parameter is the MIME type specified.

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.is('text/plain')); 
    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 ‘content-type: text/plain’, then you will see the following output on your console:
    Server listening on PORT 3000
    text/plain
    

Example 2: Filename: index.js




var express = require('express');
var app = express();
var PORT = 3000;
  
app.get('/', function (req, res) {
    console.log(req.is('text/html')); 
    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 ‘content-type: text/plain’, then you will see the following output on your console:

Server listening on PORT 3000
false

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




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