scramjet-core

Scramjet core

This is the minimal, dependency free version of scramjet used as of Scramjet version 3.0.0 as a base for scramjet and scramjet plugins.

Unless you are sure, you should be better off with using the main repo and module.

What does it do?

Scramjet is a powerful, yet simple functional stream programming framework written on top of node.js object streams that exposes a standards inspired javascript API and written fully in native ES6. Thanks to it some built in optimizations scramjet is much faster than similar frameworks in asynchronous operations (like for instance calling an API).

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 and methods, 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.
• scramjet.plugin - method for adding plugins, please see the docs
• more on plugins - a description and link.

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

Detailed DataStream docs here

Method	Description	Example
new DataStream(opts)	Create the DataStream.	DataStream example
dataStream.use(func) ⇒ *	Calls the passed in place with the stream as first argument, returns result.	use example
dataStream.tee(func) ⇒ DataStream	Duplicate the stream	tee example
dataStream.reduce(func, into) ⇒ Promise	Reduces the stream into a given accumulator	reduce example
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.filter(func) ⇒ DataStream	Filters object based on the function outcome, just like	filter example
dataStream.while(func) ⇒ DataStream	Reads the stream while the function outcome is truthy.
dataStream.until(func) ⇒ DataStream	Reads the stream until the function outcome is truthy.
dataStream.pipe(to, options) ⇒ Writable	Override of node.js Readable pipe.
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
DataStream.fromIterator(iter) ⇒ DataStream	Create a DataStream from an Iterator	fromIterator 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.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.stringify(encoding) ⇒ StringStream	Creates a string stream from the given buffer stream	stringify example
bufferStream.parse(parser) ⇒ DataStream	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.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

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 Core 3.2.0

• Improved stream merge.
• Added new methods: DataStream::until and DataStream::while.