Node.js http.ServerResponse.headersSent Property

The httpServerResponse.headersSent is an inbuilt application programming interface of class ServerResponse within the HTTP module which is used to check if the header has been sent or not.

Syntax:

const response.headersSent

Parameters: This property does not accept any arguments as a parameter.

Return Value: This property returns true if and only if headers were sent otherwise false.

Example 1: Filename-index.js

Javascript

// Node.js program to demonstrate the
// response.headersSent() method

// Importing http module
const http = require('http');

// Setting up PORT
const PORT = process.env.PORT || 3000;

// Creating http Server
const httpServer = http.createServer(
    function (request, response) {

        // Checking if response header is sent or not
        // by using headersSent method
        const value = response.headersSent;

        // Display result by using end() method
        response.end("Headers have been sent : "
            + value, 'utf8', () => {
                console.log("displaying the result...");

                httpServer.close(() => {
                    console.log("server is closed")
                })
            });
    });

// Listening to http Server
httpServer.listen(PORT, () => {
    console.log("Server is running at port 3000...");
});

Run the index.js file using the following command:

node index.js

Output:

Server is running at port 3000...
displaying the result...
server is closed

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

Headers have been sent : false

Example 2: Filename-index.js

Javascript

// Node.js program to demonstrate the
// response.headersSent() method

// Importing http module
const http = require('http');

// Request and response handler
const httpHandlers = (request, response) => {
    // Checking if response header is sent or not
    // by using headersSent method
    const value = response.headersSent;

    // Display result by using end() method
    response.end("Headers have been sent : "
        + value, 'utf8', () => {
            console.log("displaying the result...");

            httpServer.close(() => {
                console.log("server is closed")
            })
        });
};

// Creating http Server
const httpServer = http.createServer(
    httpHandlers).listen(3000, () => {
        console.log("Server is running at port 3000...");
    });

Run the index.js file using the following command:

node index.js

Output:

Server is running at port 3000...
displaying the result...
server is closed

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

Headers have been sent : false

Reference: https://nodejs.org/dist/latest-v12.x/docs/api/http.html#http_response_headerssent