options
{Object} [stream.transform
options][]- Returns: {Hash}
Creates a new Hash
object that contains a deep copy of the internal state
of the current Hash
object.
The optional options
argument controls stream behavior. For XOF hash
functions such as 'shake256'
, the outputLength
option can be used to
specify the desired output length in bytes.
An error is thrown when an attempt is made to copy the Hash
object after
its [hash.digest()
][] method has been called.
// Calculate a rolling hash.
const crypto = require('crypto');
const hash = crypto.createHash('sha256');
hash.update('one');
console.log(hash.copy().digest('hex'));
hash.update('two');
console.log(hash.copy().digest('hex'));
hash.update('three');
console.log(hash.copy().digest('hex'));
// Etc.