scramjet

What does it do?

Scramjet is a powerful, yet simple framework written on top of node.js object streams, somewhat similar to the well-known event-stream or highland module, but with a much simplier API and written fully in ES6. It is built upon the logic behind three well known javascript array operations - namingly map, filter and reduce. This means that if you've ever performed operations on an Array in JavaScript - you already know Scramjet like the back of your hand.

The main advantage of scramjet is running asynchronous operations on your data streams. First of all it allows you to perform the transformations both synchronously and asynchronously by using the same API - so now you can "map" your stream from whatever source and call any number of API's consecutively.

The benchmarks are punblished in the scramjet-benchmark repo.

Example

How about a CSV parser of all the parkings in the city of Wrocław from http://www.wroclaw.pl/open-data/...

const request = require("request");
const StringStream = require("scramjet").StringStream;

let columns = null;
request.get("http://www.wroclaw.pl/open-data/opendata/its/parkingi/parkingi.csv")
    .pipe(new StringStream())
    .split("\n")
    .parse((line) => line.split(";"))
    .pop(1, (data) => columns = data)
    .map((data) => columns.reduce((acc, id, i) => (acc[id] = data[i], acc), {}))
    .on("data", console.log.bind(console))

API Docs

Here's the list of the exposed classes, please review the specific documentation for details:

• scramjet.DataStream - the base class for all scramjet classes.
• scramjet.BufferStream - a DataStream of Buffers.
• scramjet.StringStream - a DataStream of Strings.
• scramjet.MultiStream - a DataStream of Strings.

Note that:

• Most of the methods take a callback argument that operates on the stream items.
• The callback, unless it's stated otherwise, will receive an argument with the next chunk.
• If you want to perform your operations asynchronously, return a Promise, otherwise just return the right value.

The quick reference of the exposed classes:

DataStream ⇐ stream.PassThrough

DataStream is the primary stream type for Scramjet. When you parse your stream, just pipe it you can then perform calculations on the data objects streamed through your flow.

Detailed DataStream docs here

Method	Description	Example
new DataStream(opts)	Create the DataStream.	DataStream example
dataStream.debug(func) ⇒ DataStream	Injects a debugger statement when called.	debug example
dataStream.use(func) ⇒ *	Calls the passed in place with the stream as first argument, returns result.	use example
dataStream.group(func) ⇒ DataStream	Separates execution to multiple streams using the hashes returned by the passed callback	group example
dataStream.tee(func) ⇒ DataStream	Duplicate the stream	tee example
dataStream.slice(start, end, func) ⇒ DataStream	Gets a slice of the stream to the callback function.	slice example
dataStream.accumulate(func, into) ⇒ Promise	Accumulates data into the object.	accumulate example
dataStream.reduce(func, into) ⇒ Promise	Reduces the stream into a given accumulator	reduce example
dataStream.reduceNow(func, into) ⇒ *	Reduces the stream into the given object, returning it immediately.	reduceNow example
dataStream.remap(func, Clazz) ⇒ DataStream	Remaps the stream into a new stream.	remap example
dataStream.flatMap(func, Clazz) ⇒ DataStream	Takes any method that returns any iterable and flattens the result.	flatMap example
dataStream.unshift(item) ↩︎	Pushes any data at call time
dataStream.flatten() ⇒ DataStream	A shorthand for streams of Arrays to flatten them.
dataStream.batch(count) ⇒ DataStream	Aggregates count items for microbatch processing
dataStream.each(func) ↩︎	Performs an operation on every chunk, without changing the stream
dataStream.map(func, Clazz) ⇒ DataStream	Transforms stream objects into new ones, just like Array.prototype.map	map example
dataStream.assign(func) ⇒ DataStream	Transforms stream objects by assigning the properties from the returned	assign example
dataStream.filter(func) ⇒ DataStream	Filters object based on the function outcome, just like	filter example
dataStream.shift(count, func) ⇒ DataStream	Shifts the first n items from the stream and pipes the other	shift example
dataStream.separate() ⇒ MultiStream	Splits the stream two ways	separate example
dataStream.toBufferStream(serializer) ⇒ BufferStream	Creates a BufferStream	toBufferStream example
dataStream.stringify(serializer) ⇒ StringStream	Creates a StringStream	stringify example
dataStream.toArray(initial) ⇒ Promise	Aggregates the stream into a single Array
DataStream.fromArray(arr) ⇒ DataStream	Create a DataStream from an Array	fromArray example

StringStream ⇐ DataStream

A stream of string objects for further transformation on top of DataStream.

Detailed StringStream docs here

Method	Description	Example
new StringStream(encoding)	Constructs the stream with the given encoding	StringStream example
stringStream.shift(bytes, func) ⇒ StringStream	Shifts given length of chars from the original stream	shift example
stringStream.split(splitter) ⇒ StringStream	Splits the string stream by the specified regexp or string	split example
stringStream.append(arg) ⇒ StringStream	Appends given argument to all the items.	append example
stringStream.prepend(arg) ⇒ StringStream	Prepends given argument to all the items.	prepend example
stringStream.match(splitter) ⇒ StringStream	Finds matches in the string stream and streams the match results	match example
stringStream.toBufferStream() ⇒ StringStream	Transforms the StringStream to BufferStream	toBufferStream example
stringStream.parse(parser) ⇒ DataStream	Parses every string to object	parse example
StringStream.SPLIT_LINE	A handly split by line regex to quickly get a line-by-line stream
StringStream.fromString(str, encoding) ⇒ StringStream	Creates a StringStream and writes a specific string.

BufferStream ⇐ DataStream

A factilitation stream created for easy splitting or parsing buffers

Detailed BufferStream docs here

Method	Description	Example
new BufferStream(opts)	Creates the BufferStream	BufferStream example
bufferStream.shift(chars, func) ⇒ BufferStream	Shift given number of bytes from the original stream	shift example
bufferStream.split(splitter) ⇒ BufferStream	Splits the buffer stream into buffer objects	split example
bufferStream.breakup(number) ⇒ BufferStream	Breaks up a stream apart into chunks of the specified length	breakup example
bufferStream.toStringStream(encoding) ⇒ StringStream	Creates a string stream from the given buffer stream	toStringStream example
bufferStream.parse(parser) ⇒ DataStream	[Parallel] Parses every buffer to object	parse example

MultiStream

An object consisting of multiple streams than can be refined or muxed.

Detailed MultiStream docs here

Method	Description	Example
new MultiStream(streams, options)	Crates an instance of MultiStream with the specified stream list	MultiStream example
multiStream.streams : Array	Array of all streams
multiStream.map(aFunc) ⇒ MultiStream	Returns new MultiStream with the streams returned by the tranform.	map example
multiStream.filter(func) ⇒ MultiStream	Filters the stream list and returns a new MultiStream with only the	filter example
multiStream.dedupe(cmp) ⇒ DataStream	Removes duplicate items from stream using the given hash function	dedupe example
multiStream.mux(cmp) ⇒ DataStream	Muxes the streams into a single one	mux example
multiStream.add(stream)	Adds a stream to the MultiStream	add example
multiStream.remove(stream)	Removes a stream from the MultiStream	remove example

Browserifying

Scramjet works in the browser too, there's a nice, self-contained sample in here, just run it:

    git clone https://github.com/signicode/scramjet.git
    cd scramjet
    npm install .
    cd samples/browser
    npm start # point your browser to http://localhost:30035 and open console

If you need your scramjet version for the browser, grab browserify and just run:

    browserify lib/index -standalone scramjet -o /path/to/your/browserified-scramjet.js

With this you can run your transformations in the browser, use websockets to send them back and forth. If you do and fail for some reason, please remember to be issuing those issues - as no one person can test all the use cases and I am but one person.

Usage

Scramjet uses functional programming to run transformations on your data streams in a fashion very similar to the well known event-stream node module. Most transformations are done by passing a transform function. You can write your function in two ways:

1. Synchronous

Example: a simple stream transform that outputs a stream of objects of the same id property and the length of the value string.

   datastream.map(
       (item) => ({id: item.id, length: item.value.length})
   )

1. Asynchronous (using Promises)

Example: A simple stream that fetches an url mentioned in the incoming object

   datastream.map(
       (item) => new Promise((resolve, reject) => {
           request(item.url, (err, res, data) => {
               if (err)
                   reject(err); // will emit an "error" event on the stream
               else
                   resolve(data);
           });
       })
   )

The actual logic of this transform function is as if you passed your function to the then method of a Promise resolved with the data from the input stream.

License and contributions

As of version 2.0 Scramjet is MIT Licensed.

Help wanted

The project need's your help! There's lots of work to do - transforming and muxing, joining and splitting, browserifying, modularizing, documenting and issuing those issues.

If you want to help and be part of the Scramjet team, please reach out to me, signicode on Github or email me: [e-mail].

Changelog

Scramjet 2.7.0

Implemented DataStream::group.