What is Node.js hmac.update() Method?

In this article, we will learn Node.js hmac.update() Method,This free Node.js tutorial for complete beginners will help you learn Node.js from scratch.

Node.js hmac.update() Method - ❤️Node.js Tutorials In 2024

The hmac.update() method is an inbuilt method of class HMAC within the crypto module which is used to update the data of hmac object.

Syntax:

hmac.update(data[, inputEncoding])

Parameters: This method takes the following two parameters:

data: It can be of string, Buffer, TypedArray, or DataView type. It is the data that is passed to this function.
inputEncoding: It is an optional parameter. It is the encoding of the data string.

Return Value: This method returns nothing.

Project Setup: Create a new NodeJS project and name it hmac.

mkdir hmac && cd hmac
npm init -y

Now create a .js file in your project root directory and name it index.js

Example 1:

index.js

// Node.js program to demonstrate the 
// crypto hmac.update() method 
    
// Importing crypto module 
const { createHmac } = require('crypto') 
  
// Creating and initializing algorithm and password 
const algo = 'sha256'
const secret = 'GFG Secret Key'
  
// Create an HMAC instance 
const hmac = createHmac(algo, secret) 
  
// Update the internal state of the hmac object 
hmac.update('w3wiki') 
  
// Perform the final operations 
// Return calculated hash 
const result = hmac.digest('base64') 
  
// Print the result 
console.log(`HMAC hash: ${result}`) 

Run the index.js file using the following command:

node index.js

Output:

HMAC hash: yK4+CYVa56w0Ba1g2TdY7cDM68HPXFKb+10FhnRpXFM=

Example 2:

index.js

// Node.js program to demonstrate the     
// crypto hmac.update() method 
  
// Defining myfile 
const myfile = process.argv[2]; 
  
// Includes crypto and fs module 
const crypto = require('crypto'); 
const fs = require('fs'); 
  
// Creating and initializing algorithm and password 
const algo = 'sha256'
const secret = 'GFG Secret Key'
  
// Creating Hmac 
const hmac = crypto.createHmac(algo, secret); 
  
// Creating read stream 
const readfile = fs.createReadStream(myfile); 
  
readfile.on('readable', () => { 
  
  // Calling read method to read data 
  const data = readfile.read(); 
  
  if (data) 
  
    // Updating 
    hmac.update(data); 
  else { 
  
    // Perform the final operations  
    // Return hash value 
    const result = hmac.digest('hex') 
  
    // Display result 
    console.log(`HMAC hash value of ${myfile}: ${result}`); 
  } 
});

Run the index.js file using the following command:

node index.js package.json

Output:

HMAC hash value of package.json: 38f0f975f8964343c24da940188eaeb6bb20842e3c5bf03ccb66773e98beeb73

Reference: https://nodejs.org/api/crypto.html#crypto_hmac_update_data_inputencoding