This module was inspired from mississippi.
npm install mississippi2 --savevar miss = require('mississippi2')- pipe
- merge *
- condition *
- each
- map *
- filter *
- reduce *
- split *
- spy *
- pipeline
- duplex
- through
- from
- fromValue *
- fromPromise *
- fromObservable *
- to
- toString *
- toArray *
- toPromise *
- toObservable *
- concat
- unique *
- toJSON *
- stringify *
- child *
- finished
- throttle *
- Parser *
Pipes streams together and destroys all of them if one of them closes. Calls cb with (error) if there was an error in any of the streams.
When using standard source.pipe(destination) the source will not be destroyed if the destination emits close or error. You are also not able to provide a callback to tell when the pipe has finished.
miss.pipe does these two things for you, ensuring you handle stream errors 100% of the time (unhandled errors are probably the most common bug in most node streams code)
miss.pipe is provided by require('pump')
// lets do a simple file copy
var fs = require('fs')
var read = fs.createReadStream('./original.zip')
var write = fs.createWriteStream('./copy.zip')
// use miss.pipe instead of read.pipe(write)
miss.pipe(read, write, function (err) {
if (err) return console.error('Copy error!', err)
console.log('Copied successfully')
})Return a streams that merged alll streams together and emmit parallely events. When merge readable streams, return a readable stream that reads from multiple readable streams at the same time. If you want to emits multiple other streams one after another, use merge2. When merge writable streams, retrun a writable stream that writes to multiple other writeable streams.
miss.merge is provided by require('multi-duplex-stream')
// merge readable stream
var multiRead = miss.merge([
miss.fromValue("hello"),
miss.fromValue("world")
]);
multiRead.on("data", function(data){
console.log(data); // "hello" "world" or "world" "hello"
});
multiRead.on("end", function(){
console.log("no more data");
});
// merge writable stream
var read = miss.fromValue('hello, world');
var write1 = fs.createWriteStream('./file1.txt');
var write2 = fs.createWriteStream('./file2.txt');
var multiWrite = miss.merge([write1,write2]);
read.pipe(multiWrite).on("end",function(){
// both file1 and file2 now contains "hello, world"
});Condition stream can conditionally control the flow of stream data.
Condition stream will pipe data to stream whenever condition is truthy.
If condition is falsey and elseStream is passed, data will pipe to elseStream.
After data is piped to stream or elseStream or neither, data is piped down-stream.
miss.condition is provided by require('ternary-stream')
// if the condition returns truthy, data is piped to the child stream
var condition = function (data) {
return true;
};
process.stdin
.pipe(miss.condition(condition, process.stdout))
.pipe(fs.createWriteStream('./out.txt'));
// Data will conditionally go to stdout, and always go to the file
var through2 = require('through2');
var count = 0;
var condition = function (data) {
count++;
return count % 2;
};
process.stdin
.pipe(miss.condition(condition, fs.createWriteStream('./truthy.txt'), fs.createWriteStream('./falsey.txt')))
.pipe(process.stdout);Iterate the data in stream one chunk at a time. Your each function will be called with (data, next) where data is a data chunk and next is a callback. Call next when you are ready to consume the next chunk.
Optionally you can call next with an error to destroy the stream. You can also pass the optional third argument, done, which is a function that will be called with (err) when the stream ends. The err argument will be populated with an error if the stream emitted an error.
miss.each is provided by require('stream-each')
var fs = require('fs')
var split = require('split2')
var newLineSeparatedNumbers = fs.createReadStream('numbers.txt')
var pipeline = miss.pipeline(newLineSeparatedNumbers, split())
var each = miss.each(pipeline, eachLine, done)
var sum = 0
function eachLine (line, next) {
sum += parseInt(line.toString())
next()
}
function done (err) {
if (err) throw err
console.log('sum is', sum)
}Return a stream.Transfrom instance that will call fn(chunk, index) on each stream segment.
Note you will NOT be able to skip chunks. This is intended for modification only. If you want filter the stream content, use miss.filter. This transform also does not have a flush function.
miss.map is provided by require('through2-map')
var truncate = miss.map(function (chunk) {
return chunk.slice(0, 10)
});
// Then use your map:
source.pipe(truncate).pipe(sink)Create a through2-filter instance that will call fn(chunk). If fn(chunk) returns "true" the chunk will be passed downstream. Otherwise it will be dropped.
Note you will NOT be able to alter the content of the chunks. This is intended for filtering only. If you want to modify the stream content, use either miss.through or miss.map.
miss.filter is provided by require('through2-filter')
var skip = miss.filter(function (chunk) {
// skip buffers longer than 100
return chunk.length < 100
})
// Then use your filter:
source.pipe(skip).pipe(sink)Create a Reduce instance. Works like Array.prototype.reduce meaning you can specify a fn function that takes up to three arguments: fn(previous, current, index) and you can specify an initial value.
This stream will only ever emit a single chunk. For more traditional stream.Transform filters or transforms, consider miss.through miss.filter or miss.map.
miss.reduce is provided by require('through2-reduce')
var sum = miss.reduce({objectMode: true}, function (previous, current) { return previous + current })
// Then use your reduce: (e.g. source is an objectMode stream of numbers)
source.pipe(sum).pipe(sink)Break up a stream and reassemble it so that each line is a chunk.
matcher may be a String, or a RegExp.
miss.split is provided by require('split2')
fs.createReadStream(file)
.pipe(miss.split())
.on('data', function (line) {
//each chunk now is a seperate line!
})Create a miss.spy instance that will call fn(chunk) and then silently pass through data downstream.
Note you will NOT be able to do anything but spy and abort the stream pipeline. To do any filtering or transformations you should consider miss.through miss.filter or miss.map.
miss.spy is provided by require('through2-spy')
var count = 0;
var countChunks = miss.spy(function (chunk) {
count++
});
// Then use your spy:
source.pipe(countChunks).pipe(sink);Builds a pipeline from all the transform streams passed in as arguments by piping them together and returning a single stream object that lets you write to the first stream and read from the last stream.
If any of the streams in the pipeline emits an error or gets destroyed, or you destroy the stream it returns, all of the streams will be destroyed and cleaned up for you.
miss.pipeline is provided by require('pumpify')
// first create some transform streams (note: these two modules are fictional)
var imageResize = require('image-resizer-stream')({width: 400})
var pngOptimizer = require('png-optimizer-stream')({quality: 60})
// instead of doing a.pipe(b), use pipelin
var resizeAndOptimize = miss.pipeline(imageResize, pngOptimizer)
// `resizeAndOptimize` is a transform stream. when you write to it, it writes
// to `imageResize`. when you read from it, it reads from `pngOptimizer`.
// it handles piping all the streams together for you
// use it like any other transform stream
var fs = require('fs')
var read = fs.createReadStream('./image.png')
var write = fs.createWriteStream('./resized-and-optimized.png')
miss.pipe(read, resizeAndOptimize, write, function (err) {
if (err) return console.error('Image processing error!', err)
console.log('Image processed successfully')
})Take two separate streams, a writable and a readable, and turn them into a single duplex (readable and writable) stream.
The returned stream will emit data from the readable. When you write to it it writes to the writable.
You can either choose to supply the writable and the readable at the time you create the stream, or you can do it later using the .setWritable and .setReadable methods and data written to the stream in the meantime will be buffered for you.
miss.duplex is provided by require('duplexify')
// lets spawn a process and take its stdout and stdin and combine them into 1 stream
var child = require('child_process')
// @- tells it to read from stdin, --data-binary sets 'raw' binary mode
var curl = child.spawn('curl -X POST --data-binary @- http://foo.com')
// duplexCurl will write to stdin and read from stdout
var duplexCurl = miss.duplex(curl.stdin, curl.stdout)#####var transformer = miss.through([options, transformFunction, flushFunction])
Make a custom transform stream.
The options object is passed to the internal transform stream and can be used to create an objectMode stream (or use the shortcut miss.through.obj([...]))
The transformFunction is called when data is available for the writable side and has the signature (chunk, encoding, cb). Within the function, add data to the readable side any number of times with this.push(data). Call cb() to indicate processing of the chunk is complete. Or to easily emit a single error or chunk, call cb(err, chunk)
The flushFunction, with signature (cb), is called just before the stream is complete and should be used to wrap up stream processing.
miss.through is provided by require('through2')
var fs = require('fs')
var read = fs.createReadStream('./boring_lowercase.txt')
var write = fs.createWriteStream('./AWESOMECASE.TXT')
// Leaving out the options object
var uppercaser = miss.through(
function (chunk, enc, cb) {
cb(null, chunk.toString().toUpperCase())
},
function (cb) {
cb(null, 'ONE LAST BIT OF UPPERCASE')
}
)
miss.pipe(read, uppercaser, write, function (err) {
if (err) return console.error('Trouble uppercasing!')
console.log('Splendid uppercasing!')
})#####miss.from([opts], read)
Make a custom readable stream.
opts contains the options to pass on to the ReadableStream constructor e.g. for creating a readable object stream (or use the shortcut miss.from.obj([...])).
Returns a readable stream that calls read(size, next) when data is requested from the stream.
sizeis the recommended amount of data (in bytes) to retrieve.next(err, chunk)should be called when you're ready to emit more data.
miss.from is provided by require('from2')
function fromString(string) {
return miss.from(function(size, next) {
// if there's no more content
// left in the string, close the stream.
if (string.length <= 0) return next(null, null)
// Pull in a new chunk of text,
// removing it from the string.
var chunk = string.slice(0, size)
string = string.slice(size)
// Emit "chunk" from the stream.
next(null, chunk)
})
}
// pipe "hello world" out
// to stdout.
fromString('hello world').pipe(process.stdout)#####miss.fromValue(value)
Create streams from (single) arbitrary Javascript values like strings, functions, arrays, etc.
Please Note miss.fromValue are Readable streams.
miss.fromValue is provided by require('stream-from-value')
miss.fromValue('some string')
.pipe(process.stdout); // output: some string
miss.fromValue(new Buffer('some string'))
.pipe(process.stdout); // output: some string
// Stream of (arbitrary) Javascript Value
miss.fromValue.obj(['some', 'mixed', 'array', 42]).on('data', function(data){
console.log(data); // output: [ 'some', 'mixed', 'array', 42 ]
});#####miss.fromPromise(promise)
Make a Readable streams from ECMAScript 2015 Promises that return Javascript values like numbers, strings, objects, functions.
miss.fromPromise is provided by require('stream-from-promise')
// `String promises
var stringPromise = new Promise(function(resolve, reject){
setTimeout(function(){
resolve('strrrring!');
}, 500);
});
miss.fromPromise(stringPromise).pipe(process.stdout); // => output: strrrring!
// Buffer promises
var bufferPromise = new Promise(function(resolve, reject){
setTimeout(function(){
resolve(new Buffer('buff!'));
}, 500);
});
StreamFromPromise(bufferPromise)
.pipe(process.stdout); // output: buff!#####miss.fromObservable(observable, stream, [encoding])
Writes an observable sequence to a writable stream.
Arguments
observable(Observable): Observable sequence to write to a stream.stream(Stream): The stream to write to.[encoding](String): The encoding of the item to write.
Returns
- (Disposable): The subscription handle.
miss.fromObsesrvable is provided by require("rx-node").writeToStream
var Rx = require('rx');
var source = Rx.Observable.range(0, 5);
var subscription = miss.fromObsesrvable(source, process.stdout, 'utf8');
// => 01234#####miss.to([options], write, [flush])
Make a custom writable stream.
opts contains the options to pass on to the WritableStream constructor e.g. for creating a readable object stream (or use the shortcut miss.to.obj([...])).
Returns a writable stream that calls write(data, enc, cb) when data is written to the stream.
datais the received data to write the destination.encencoding of the piece of data received.next(err, chunk)should be called when you're ready to write more data, or encountered an error.
flush(cb) is called before finish is emitted and allows for cleanup steps to occur.
miss.to is provided by require('flush-write-stream')
var ws = miss.to(write, flush)
ws.on('finish', function () {
console.log('finished')
})
ws.write('hello')
ws.write('world')
ws.end()
function write (data, enc, cb) {
// i am your normal ._write method
console.log('writing', data.toString())
cb()
}
function flush (cb) {
// i am called before finish is emitted
setTimeout(cb, 1000) // wait 1 sec
}If you run the above it will produce the following output
writing hello
writing world
(nothing happens for 1 sec)
finished
#####miss.toString(stream [, callback])
Pipe a stream into a string, collect value with callback or promise.
Collects stream data into a string. Executes optional callback(err, string). Returns a promise.
miss.toString is provided by require('stream-to-string')
// with callback
var stream = miss.through();
miss.toString(stream, function (err, msg) {
console.log(msg)
})
// or with promises
miss.toString(stream).then(function (msg) {
console.log(msg)
})
stream.write('this is a')
stream.write(' test')
stream.end()#####miss.toArray([stream], [callback(err, arr)])
Concatenate a readable stream's data into a single array.
Returns all the data objects in an array. This is useful for streams in object mode if you want to just use an array.
miss.toArray is provided by require('stream-to-array')
// with callback
var stream = miss.through();
miss.toArray(stream, function (err, msg) {
console.log(msg)
})
// or with promises
miss.toArray(stream).then(function (msg) {
console.log(msg)
})
stream.write('this is a')
stream.write(' test')
stream.end()#####miss.toPromise(stream)
Convert streams (readable or writable) to promises.
miss.toPromise is provided by require('stream-to-promise2')
miss.toPromise(readableStream).then(function (buffer) {
// buffer.length === 3
});
readableStream.emit('data', new Buffer());
readableStream.emit('data', new Buffer());
readableStream.emit('data', new Buffer());
readableStream.emit('end'); // promise is resolved here#####miss.toObservable(stream, finishEventName, dataEventName)
Converts a flowing readable to an Observable sequence.
Arguments
stream(Stream): A stream to convert to a observable sequence.[dataEventName](String): Event that notifies about incoming data. ("data" by default)
Returns
- (Observable): An observable sequence which fires on each 'data' event as well as handling 'error' and 'end' events.
miss.toObservable is provided by require("rx-node").writeToStream
var subscription = miss.toObservable(process.stdin)
.subscribe(function (x) { console.log(x); });
// => r<Buffer 72>
// => x<Buffer 78>#####var concat = miss.concat(cb)
Returns a writable stream that concatenates all data written to the stream and calls a callback with the single result.
Calling miss.concat(cb) returns a writable stream. cb is called when the writable stream is finished, e.g. when all data is done being written to it. cb is called with a single argument, (data), which will containe the result of concatenating all the data written to the stream.
Note that miss.concat will not handle stream errors for you. To handle errors, use miss.pipe or handle the error event manually.
miss.concat is provided by require('concat-stream')
var fs = require('fs')
var concat = require('concat-stream')
var readStream = fs.createReadStream('cat.png')
var concatStream = concat(gotPicture)
readStream.on('error', handleError)
readStream.pipe(concatStream)
function gotPicture(imageBuffer) {
// imageBuffer is all of `cat.png` as a node.js Buffer
}
function handleError(err) {
// handle your error appropriately here, e.g.:
console.error(err) // print the error to STDERR
process.exit(1) // exit program with non-zero exit code
}#####miss.unique([fn])
Filter duplicates from a stream based on a hashing fn(chunk). By default, this hashing function is:
sha256sum(JSON.stringify(doc))miss.unique is provided by require('unique-hash-stream')
var stream = miss.through();
var hashFn = function(chunk){
return chunk;
};
stream.pipe(miss.unique(hashFn)).pipe(process.stdout);
stream.write("a");
stream.write("a");
stream.write("b");
stream.end();#####miss.toJSON(stream, callback)
Read all from stream, then JSON.parse and call callback(err, json) with the result. If there's an Error in the stream itself, or parsing the JSON, an error will be passed.
miss.toJSON is provided by require('stream-to-json')
var request = require('request');
miss.toJSON(request('/some/url.json'), function(err, json) {
if (err) throw err;
console.log(json);
});#####miss.stringify([options])
Similar to JSONStream.stringify() except it is, by default, a binary stream, and it is a streams2 implementation.
Please NOTE : The main use case for this is to stream a database query to a web client. This is meant to be used only with arrays, not objects.
Separators
- The stream always starts with '[\n'.
- Documents are separated by '\n,\n'.
- The stream is terminated with '\n]\n'.
miss.stringify is provided by require('streaming-json-stringify')
app.get('/things', function (req, res, next) {
res.setHeader('Content-Type', 'application/json; charset=utf-8')
db.things.find()
.stream()
.pipe(miss.stringify())
.pipe(res)
})will yield something like
[
{"_id":"123412341234123412341234"}
,
{"_id":"123412341234123412341234"}
]
#####miss.child(command, [args], [options])
Spawn a child process as a duplex stream.
Convenience wrapper for:
new Child_Process().spawn(command, [args], [options])miss.child is provided by require('duplex-child-process')
var toJPEG = miss.child.spawn('convert', ['-', 'JPEG:-'])
var getFormat = miss.child.spawn('identify', ['-format', '%m', '-'])
fs.createReadStream('img.png')
.pipe(toJPEG)
.pipe(getFormat)
.once('readable', function () {
var format = this.read().toString('utf8')
assert.equal(format, 'JPEG')
})#####miss.finished(stream, cb)
Waits for stream to finish or error and then calls cb with (err). cb will only be called once. err will be null if the stream finished without error, or else it will be populated with the error from the streams error event.
This function is useful for simplifying stream handling code as it lets you handle success or error conditions in a single code path. It's used internally miss.pipe.
miss.finished is provided by require('end-of-stream')
var copySource = fs.createReadStream('./movie.mp4')
var copyDest = fs.createWriteStream('./movie-copy.mp4')
copySource.pipe(copyDest)
miss.finished(copyDest, function(err) {
if (err) return console.log('write failed', err)
console.log('write success')
})#####miss.throttle(n)
This stream offers a Throttle passthrough stream class, which allows you to write data to it and it will be passed through in n bytes per second. It can be useful for throttling HTTP uploads or to simulate reading from a file in real-time, etc.
miss.throttle is provided by require("throttle")
// throttling stdin at 1 byte per second and outputting the data to stdout:
process.stdin.pipe(miss.throttle(1)).pipe(process.stdout);#####miss.Parser
This tool offers the stream-parser mixin, which provides an easy-to-use API for parsing bytes from Writable and/or Transform stream instances. This module is great for implementing streaming parsers for standardized file formats.
For Writable streams, the parser takes control over the _write callback function. For Transform streams, the parser controls the _transform callback function.
The Parser stream mixin works with either Writable or Transform stream
instances/subclasses. Provides a convenient generic "parsing" API:
_bytes(n, cb) - buffers "n" bytes and then calls "cb" with the "chunk"
_skipBytes(n, cb) - skips "n" bytes and then calls "cb" when doneIf you extend a Transform stream, then the _passthrough() function is also
added:
_passthrough(n, cb) - passes through "n" bytes untouched and then calls "cb"Buffers n bytes and then invokes cb once that amount has been collected.
Skips over the next n bytes and then invokes cb once that amount has been
discarded.
Passes through n bytes to the readable side of this stream untouched,
then invokes cb once that amount has been passed through. This function is only defined
when stream-parser is extending a Transform stream.
miss.Parser is provided by require('stream-parser')
Let's create a quick Transform stream subclass that utilizes the parser's
_bytes() and _passthrough() functions to parse a theoretical file format that
has an 8-byte header we want to parse, and then pass through the rest of the data.
var inherits = require('util').inherits;
var Transform = require('stream').Transform;
// create a Transform stream subclass
function MyParser () {
Transform.call(this);
// buffer the first 8 bytes written
this._bytes(8, this.onheader);
}
inherits(MyParser, Transform);
// mixin stream-parser into MyParser's `prototype`
miss.Parser(MyParser.prototype);
// invoked when the first 8 bytes have been received
MyParser.prototype.onheader = function (buffer, output) {
// parse the "buffer" into a useful "header" object
var header = {};
header.type = buffer.readUInt32LE(0);
header.name = buffer.toString('utf8', 4);
this.emit('header', header);
// it's usually a good idea to queue the next "piece" within the callback
this._passthrough(Infinity);
};
// now we can *use* it!
var parser = new MyParser();
parser.on('header', function (header) {
console.error('got "header"', header);
});
process.stdin.pipe(parser).pipe(process.stdout);