How to Create Hash From String in JavaScript?

To create a hash from a string in JavaScript, you can use hashing algorithms like MD5, SHA-1, or SHA-256. Here are the different methods to create HASH from string in JavaScript.

1. Using JavaScript charCodeAt() method

The JavaScript str.charCodeAt() method returns a Unicode character set code unit of the character present at the index in the string specified as the argument. The index number ranges from 0 to n-1, where n is the string’s length.

Syntax

str.charCodeAt(index)

function toHash(string) {

    let hash = 0;

    if (string.length == 0) return hash;

    for (i = 0; i < string.length; i++) {
        char = string.charCodeAt(i);
        hash = ((hash << 5) - hash) + char;
        hash = hash & hash;
    }

    return hash;
}

// String printing in hash
let gfg = "GeeksforGeeks"
console.log(toHash(gfg));

-1119635595

2. Using crypto.createHash() method

The crypto.createHash() method in Node.js is used to create a hash object that can generate a hash of a given data using a specified algorithm, such as SHA-256, SHA-512, or MD5.

Syntax

const crypto = require('crypto');
const hash = crypto.createHash(algorithm);

• algorithm: A string representing the hashing algorithm to be used (e.g., 'sha256', 'sha512', 'md5').
• hash: The hash object that allows the hashing process to be updated with data and then generates the final hash.

const crypto = require('crypto'),
    hash = crypto.getHashes();

x = "Geek"
hashPwd = crypto.createHash('sha1')
    .update(x).digest('hex');

console.log(hashPwd);

321cca8846c784b6f2d6ba628f8502a5fb0683ae

In this example

• Import crypto module: Allows access to cryptographic functions.
• Define input string: Sets the string to be hashed.
• Create SHA-1 hash: Creates a SHA-1 hash and converts the input string into its hex representation.
• Log the hash: Prints the resulting hash of "Geek" to the console.

3. Using JavaScript String's reduce() Method

The reduce() method in JavaScript is typically used with arrays to reduce them to a single value. It can also be used with strings to create custom operations, like generating a simple hash from a string.

function toHash(string) {
    return string.split('').reduce((hash, char) => {
        return char.charCodeAt(0) + (hash << 6) + (hash << 16) - hash;
    }, 0);
}

let gfg = "GeeksforGeeks";
console.log(toHash(gfg));

-2465134923

In this example:

• split(''): This converts the string into an array of characters.
• reduce(): The reduce() method loops through the array, performing a cumulative operation on each character. The operation here is to add the character's ASCII value to an accumulator.
• char.charCodeAt(0): This gets the ASCII code of each character.
• Accumulator (acc): This starts at 0 and keeps adding the ASCII values of each character.

4. Using SHA-256 algorithm

The crypto module in Node.js allows developers to work with cryptographic operations like hashing. The createHash() method is commonly used to create a hash of a given input using algorithms like SHA-256.

const crypto = require('crypto');

function createSHA256Hash(inputString) {
    const hash = crypto.createHash('sha256');
    hash.update(inputString);
    return hash.digest('hex');
}

// Example usage
const inputString = "Hello, World!";
const hashValue = createSHA256Hash(inputString);
console.log(hashValue);

Output

2cf24dba5fb0a30e26e83b2ac5b9e29e1b161e5c1fa7425e73043362938b9824

5. Using the crypto.subtle API (Browser Environment)

The crypto.subtle API is built into modern browsers and provides a way to perform cryptographic operations like hashing. Here is how you can generate a SHA-256 hash in the browser using crypto.subtle

async function hashString(inputString) {
    const encoder = new TextEncoder();
    const data = encoder.encode(inputString); 
    const hashBuffer = await crypto.subtle.digest('SHA-256', data); 

    const hashArray = Array.from(new Uint8Array(hashBuffer)); 
    const hashHex = hashArray.map(byte => byte.toString(16).padStart(2, '0')).join(''); 

    return hashHex;
}

hashString("Hello, World!").then(hash => {
    console.log("Hash: " + hash);
});

Output

Hash: a591a6d40bf420404a011733cfb7b190d62c65bf0bcda7c8a660e3a1b3cfbf1b

In this example

• The TextEncoder converts the string into a byte array.
• The crypto.subtle.digest() method performs the SHA-256 hashing.
• The result is a ArrayBuffer, which we convert to an array of bytes and then to a hexadecimal string.