yauzl unzipping with Promises

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yauzl unzipping with Promises

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Promisified version of yauzl for unzipping ZIP files.


npm install yauzl-promise


open() / fromFd() / fromBuffer() / fromRandomAccessReader()

These methods all work as before, but return a Promise rather than taking a callback.
const yauzl = require( 'yauzl-promise' );

const zipFile = await yauzl.open( '/path/to/file' );

lazyEntries option is automatically enabled. Get file entries using methods listed below.
autoClose option is automatically disabled. ZipFiles must be closed manually with .close().


Closes file and returns Promise which resolves when all streams are closed.
Files must be closed when finished with to avoid resource leakages.
const zipFile = await yauzl.open( '/path/to/file' );
await zipFile.close();


Same as original yauzl method, but returning a promise. Promise resolves to an instance of yauzl.Entry, or rejects if there is an error.
const entry = await zipFile.readEntry();
console.log( entry );

Calling .readEntry() again returns the next entry. When there are no entries left, it returns null.

zipFile.readEntries( [numEntries] )

Read several entries and return as an array.
const entries = await zipFile.readEntries( 3 );
entries.forEach( console.log );

If numEntries is 0, null or undefined, reading will continue until all entries are read.
WARNING: This is dangerous. If ZIP contains a large number of files, could lead to crash due to out of memory. Use .walkEntries() instead.

zipFile.walkEntries( callback [, numEntries] )

Read several entries and call callback for each.
If callback returns a promise, the promise is awaited before reading the next entry. If callback throws an error or returns a rejected promise, walking stops and the promise returned by .walkEntries() is rejected.
Returns a promise which resolves when all have been read.
await zipFile.walkEntries( entry => {
	console.log( entry );
} );
console.log( 'Done' );

If numEntries is 0, null or undefined, reading will continue until all entries are read.

zipFile.openReadStream( entry [, options] )

Same as original method but returns promise of a stream.
const readStream = await zipFile.openReadStream( entry );
readStream.pipe( writeStream );

entry.openReadStream( [options] )

As above, but called on an Entry object.
const entry = await zipFile.readEntry();
const readStream = await entry.openReadStream();
readStream.pipe( writeStream );


ZipFile objects are from a subclass of yauzl's original ZipFile class. They are event emitters but do not emit any of the events original yauzl module emits (entry, end, close or error).
These events are replaced by the resolution/rejection of promises returned by the methods listed above.
If an error event is emitted unexpectedly within yauzl at a time when no operation (readEntry() etc) is in progress, that event is consumed to prevent the process from crashing. The next time readEntry(), close() or openReadStream() is called, the promise returned from that method will reject with the previously emitted error.


Alternative Promise implementation

Promises returned by default are native JS Promises.
.usePromise() returns a new yauzl object where the methods return promises from the specified Promise constructor.
const Bluebird = require( 'bluebird' );
const yauzl = require( 'yauzl-promise' ).usePromise( Bluebird );

const p = yauzl.open( '/path/to/file' );
console.log( p instanceof Bluebird ); // true

NB This does not alter the original yauzl object, only the one returned from .usePromise().
const Bluebird = require( 'bluebird' );
const yauzl = require( 'yauzl-promise' )
const yauzlBluebird = yauzl.usePromise( Bluebird );

const p = yauzl.open( '/path/to/file' );
console.log( p instanceof Bluebird ); // false

const p = yauzlBluebird.open( '/path/to/file' );
console.log( p instanceof Bluebird ); // true

Using another version of yauzl

.useYauzl() method promisifies a specific yauzl object.
Only useful if you have a modified version of yauzl which you want to promisify.
const yauzlCrc = require( 'yauzl-crc' );
const yauzl = require( 'yauzl-promise' ).useYauzl( yauzlCrc );

The yauzl object passed is cloned before it is modified, unless you set clone option to false:
const yauzlFork = require('my-yauzl-fork');
const yauzl = require( 'yauzl-promise' ).useYauzl( yauzlFork, { clone: false } );
console.log( yauzl == yauzlFork ); // true


Use npm test to run the tests. Use npm run cover to check coverage.


See changelog.md


If you discover a bug, please raise an issue on Github. https://github.com/overlookmotel/yauzl-promise/issues


Pull requests are very welcome. Please:
  • ensure all tests pass before submitting PR
  • add an entry to changelog
  • add tests for new features
  • document new functionality/API additions in README