Express.js res.headersSent Property
The res.headersSent property is a boolean property that indicates if the app sent HTTP headers for the response.
Syntax:
res.headersSent
Parameter: No parameters.
Return Value: This property returns a Boolean value either True or False.
Installation of express module:
- You can visit the link to Install 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 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
Example 1: Filename: index.js
var express = require( 'express' ); var app = express(); var PORT = 3000; app.get( '/' , function (req, res) { // Before res.send() console.log(res.headersSent); res.send( 'OK' ); }); app.listen(PORT, function (err){ if (err) console.log(err); console.log( "Server listening on PORT" , PORT); }); |
Steps to run the program:
- The project structure will look like this:
- Make sure you have installed express module using the following command:
npm install express
- Run index.js file using below command:
node index.js
Output:
Server listening on PORT 3000
-
Now open your browser and go to http://localhost:3000/, now you can see the following output on your console:
Server listening on PORT 3000 false
Example 2: Filename: index.js
var express = require( 'express' ); var app = express(); var PORT = 3000; app.get( '/' , function (req, res) { res.send( 'OK' ); // After res.send() console.log(res.headersSent); }); 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
Output:
Now open your browser and make GET request to http://localhost:3000, now you can see the following output on your console:
Server listening on PORT 3000 true
Reference: https://expressjs.com/en/4x/api.html#res.headersSent
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