Node.js crypto.createHash() Method

The crypto.createHash() method is used to create a Hash object that can be used to create hash digests by using the stated algorithm. 

Syntax:

crypto.createHash( algorithm, options )

Parameters: This method accept two parameters as mentioned above and described below:

• algorithm: It is dependent on the accessible algorithms which are favored by the version of OpenSSL on the platform. It returns string. The examples are sha256, sha512, etc.
• options: It is optional parameter and is used to control stream behavior. It returns an object. Moreover, For XOF hash functions like ‘shake256’, the option outputLength can be used to determine the required output length in bytes.

Return Type: It returns Hash object. 

Below examples illustrate the use of crypto.createHash() method in Node.js: 

Example 1:

javascript

// Node.js program to demonstrate the
// crypto.createHash() method

// Includes crypto module
const crypto = require('crypto');

// Defining key
const secret = 'Hi';

// Calling createHash method
const hash = crypto.createHash('sha256', secret)

                   // updating data
                   .update('How are you?')

                   // Encoding to be used
                   .digest('hex');

// Displays output
console.log(hash);

Output:

df287dfc1406ed2b692e1c2c783bb5cec97eac53151ee1d9810397aa0afa0d89

Example 2:

javascript

// Node.js program to demonstrate the
// crypto.createHash() method

// Defining filename
const filename = process.argv[1];

// Includes crypto and  fs module
const crypto = require('crypto');
const fs = require('fs');

// Creating Hash
const hash = crypto.createHash('sha256', 'Geeksforgeeks');

// Creating read stream
const input = fs.createReadStream(filename);

input.on('readable', () => {

 // Calling read method to read data
  const data = input.read();
  if (data)

    // Updating
    hash.update(data);
  else
   {
    // Encoding and displaying filename
    console.log(`${hash.digest('base64')} ${filename}`);
  }
});
console.log("Program done!");

Output:

Program done!
n95mt3468ZzAIwu/bbNU7dej6CoFkDRcNaJo7rGpLF4= index.js

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