SubtleCrypto.digest

The SubtleCrypto.digest() method returns a Promise of a digest generated from the hash function and text given as parameters.

Syntax

var hash = crypto.subtle.digest(algo, buffer);

Parameters

• algo is a DOMString defining the hash function to use. Supported values are: SHA-1, SHA-256, SHA-384, and SHA-512.
• buffer is a ArrayBuffer or an ArrayBufferView containing the data to be hashed using the hashing algorithm.

Return value

• hash is a Promise that returns the hash on success.

Example

Here's an example that computes the sha256 of a string and display its hex digest.

function sha256(str) {
  // We transform the string into an arraybuffer.
  var buffer = new TextEncoder("utf-8").encode(str);
  return crypto.subtle.digest("SHA-256", buffer).then(function (hash) {
    return hex(hash);
  });
}

function hex(buffer) {
  var hexCodes = [];
  var view = new DataView(buffer);
  for (var i = 0; i < view.byteLength; i += 4) {
    // Using getUint32 reduces the number of iterations needed (we process 4 bytes each time)
    var value = view.getUint32(i)
    // toString(16) will give the hex representation of the number without padding
    var stringValue = value.toString(16)
    // We use concatenation and slice for padding
    var padding = '00000000'
    var paddedValue = (padding + stringValue).slice(-padding.length)
    hexCodes.push(paddedValue);
  }

  // Join all the hex strings into one
  return hexCodes.join("");
}

sha256("foobar").then(function(digest) {
  console.log(digest);
}); // outputs "c3ab8ff13720e8ad9047dd39466b3c8974e592c2fa383d4a3960714caef0c4f2"

And an example using async/await.

async function sha256(message) {
    const msgBuffer = new TextEncoder('utf-8').encode(message);                     // encode as UTF-8
    const hashBuffer = await crypto.subtle.digest('SHA-256', msgBuffer);            // hash the message
    const hashArray = Array.from(new Uint8Array(hashBuffer));                       // convert ArrayBuffer to Array
    const hashHex = hashArray.map(b => ('00' + b.toString(16)).slice(-2)).join(''); // convert bytes to hex string
    return hashHex;
}

sha256('abc').then(hash => console.log(hash));

const hash = await sha256('abc');

Specifications

Specification	Status	Comment
Web Cryptography API The definition of 'SubtleCrypto.digest()' in that specification.	Candidate Recommendation	Initial definition.

Browser compatibility

See also

• Crypto and Crypto.subtle.
• SubtleCrypto, the interface it belongs to.