Hash
The Hash class is a utility for creating hash digests of data. It can be used in one of two ways:
As a
streamthat is both readable and writable, where data is written to produce a computed hash digest on the readable side, orUsing the
hash.update()andhash.digest()methods to produce the computed hash.
The {@link createHash} method is used to create Hash instances. Hashobjects are not to be created directly using the new keyword.
Example: Using Hash objects as streams:
const {
createHash,
} = await import('node:crypto');
const hash = createHash('sha256');
hash.on('readable', () => {
// Only one element is going to be produced by the
// hash stream.
const data = hash.read();
if (data) {
console.log(data.toString('hex'));
// Prints:
// 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50
}
});
hash.write('some data to hash');
hash.end();Example: Using Hash and piped streams:
import { createReadStream } from 'node:fs';
import { stdout } from 'node:process';
const { createHash } = await import('node:crypto');
const hash = createHash('sha256');
const input = createReadStream('test.js');
input.pipe(hash).setEncoding('hex').pipe(stdout);Example: Using the hash.update() and hash.digest() methods:
const {
createHash,
} = await import('node:crypto');
const hash = createHash('sha256');
hash.update('some data to hash');
console.log(hash.digest('hex'));
// Prints:
// 6a2da20943931e9834fc12cfe5bb47bbd9ae43489a30726962b576f4e3993e50Since
v0.1.92
Properties
If false then the stream will automatically end the writable side when the readable side ends. Set initially by the allowHalfOpen constructor option, which defaults to true.
Returns whether the stream was destroyed or errored before emitting 'end'.
Returns whether 'data' has been emitted.
Getter for the property encoding of a given Readable stream. The encoding property can be set using the {@link setEncoding} method.
Becomes true when 'end' event is emitted.
This property reflects the current state of a Readable stream as described in the Three states section.
Returns the value of highWaterMark passed when creating this Readable.
This property contains the number of bytes (or objects) in the queue ready to be read. The value provides introspection data regarding the status of the highWaterMark.
Getter for the property objectMode of a given Readable stream.
Is true if it is safe to call writable.write(), which means the stream has not been destroyed, errored, or ended.
Number of times writable.uncork() needs to be called in order to fully uncork the stream.
Is true after writable.end() has been called. This property does not indicate whether the data has been flushed, for this use writable.writableFinished instead.
Is set to true immediately before the 'finish' event is emitted.
Return the value of highWaterMark passed when creating this Writable.
This property contains the number of bytes (or objects) in the queue ready to be written. The value provides introspection data regarding the status of the highWaterMark.
Is true if the stream's buffer has been full and stream will emit 'drain'.
Getter for the property objectMode of a given Writable stream.
Functions
Event emitter The defined events on documents including:
This method returns a new stream with chunks of the underlying stream paired with a counter in the form [index, chunk]. The first index value is 0 and it increases by 1 for each chunk produced.
Creates a new Hash object that contains a deep copy of the internal state of the current Hash object.
Destroy the stream. Optionally emit an 'error' event, and emit a 'close' event (unless emitClose is set to false). After this call, the readable stream will release any internal resources and subsequent calls to push() will be ignored.
This method returns a new stream with the first limit chunks dropped from the start.
Calling the writable.end() method signals that no more data will be written to the Writable. The optional chunk and encoding arguments allow one final additional chunk of data to be written immediately before closing the stream.
Returns an array listing the events for which the emitter has registered listeners. The values in the array are strings or Symbols.
This method is similar to Array.prototype.every and calls fn on each chunk in the stream to check if all awaited return values are truthy value for fn. Once an fn call on a chunk awaited return value is falsy, the stream is destroyed and the promise is fulfilled with false. If all of the fn calls on the chunks return a truthy value, the promise is fulfilled with true.
This method allows filtering the stream. For each chunk in the stream the fn function will be called and if it returns a truthy value, the chunk will be passed to the result stream. If the fn function returns a promise - that promise will be awaited.
This method is similar to Array.prototype.find and calls fn on each chunk in the stream to find a chunk with a truthy value for fn. Once an fn call's awaited return value is truthy, the stream is destroyed and the promise is fulfilled with value for which fn returned a truthy value. If all of the fn calls on the chunks return a falsy value, the promise is fulfilled with undefined.
This method returns a new stream by applying the given callback to each chunk of the stream and then flattening the result.
This method allows iterating a stream. For each chunk in the stream the fn function will be called. If the fn function returns a promise - that promise will be awaited.
Returns the current max listener value for the EventEmitter which is either set by emitter.setMaxListeners(n) or defaults to {@link defaultMaxListeners}.
The iterator created by this method gives users the option to cancel the destruction of the stream if the for await...of loop is exited by return, break, or throw, or if the iterator should destroy the stream if the stream emitted an error during iteration.
This method allows mapping over the stream. The fn function will be called for every chunk in the stream. If the fn function returns a promise - that promise will be awaited before being passed to the result stream.
The readable.read() method reads data out of the internal buffer and returns it. If no data is available to be read, null is returned. By default, the data is returned as a Buffer object unless an encoding has been specified using the readable.setEncoding() method or the stream is operating in object mode.
This method calls fn on each chunk of the stream in order, passing it the result from the calculation on the previous element. It returns a promise for the final value of the reduction.
The writable.setDefaultEncoding() method sets the default encoding for a Writable stream.
The readable.setEncoding() method sets the character encoding for data read from the Readable stream.
By default EventEmitters will print a warning if more than 10 listeners are added for a particular event. This is a useful default that helps finding memory leaks. The emitter.setMaxListeners() method allows the limit to be modified for this specific EventEmitter instance. The value can be set to Infinity (or 0) to indicate an unlimited number of listeners.
This method is similar to Array.prototype.some and calls fn on each chunk in the stream until the awaited return value is true (or any truthy value). Once an fn call on a chunk awaited return value is truthy, the stream is destroyed and the promise is fulfilled with true. If none of the fn calls on the chunks return a truthy value, the promise is fulfilled with false.
This method returns a new stream with the first limit chunks.
This method allows easily obtaining the contents of a stream.
The readable.unpipe() method detaches a Writable stream previously attached using the {@link pipe} method.
Passing chunk as null signals the end of the stream (EOF) and behaves the same as readable.push(null), after which no more data can be written. The EOF signal is put at the end of the buffer and any buffered data will still be flushed.
Updates the hash content with the given data, the encoding of which is given in inputEncoding. If encoding is not provided, and the data is a string, an encoding of 'utf8' is enforced. If data is a Buffer, TypedArray, orDataView, then inputEncoding is ignored.
Prior to Node.js 0.10, streams did not implement the entire node:stream module API as it is currently defined. (See Compatibility for more information.)
The writable.write() method writes some data to the stream, and calls the supplied callback once the data has been fully handled. If an error occurs, the callback will be called with the error as its first argument. The callback is called asynchronously and before 'error' is emitted.