spicy-transducers

JavaScript library for composable algorithmic transformations.

Heavily inspired by Clojure Transducers, in case it was not obvious enough.

Be warned: Still in very early stage of development. Use at your own risk.

Why

Using transducers decouples data transformations from the actual data being transformed so that they can be easily composed and reused.

Install

npm install --save spicy-transducers
# or
yarn add spicy-transducers

Function Docs

Functions are grouped and exported based on the data type that they operate on.

Any

Name	Usage	Notes
chain	chain(fn1, fn1, ...fnN)(value)	Chain n functions and provide the initial value to be passed.
constant	constant(value)	Creates a constant function.
fallback	fallback(fallbackValue)(testValue)	Enables you to always have a fallback value if testValue is null or undefined.
identity	identity(value)	An identity function.

Array

Name	Usage	Notes
map	map(mapFunction)(array)	Map function can use the same signature as Array.prototype.map().
reduce	reduce(reduceFunction, defaultValue)(array)	Reduce function can have the same signature as Array.prototype.reduce().
pop	pop(array)	Returns a new array, with the previous head removed.
push	push(value)(array)	Returns a new array, with the new value pushed as the head.
get	get(index)(array)
set	set(index, value)(array)
update	update(index, updateFn)(array)	The update function will get the current value of the specified index as it’s argument.

Number

Name	Usage
getNthFrom	get(array)(index)

Object

Name	Usage	Notes
callMethod	call(methodName)(argument1, argument2, ...argumentN)(object)	Make sure the method exists, otherwise TypeError: value[methodName] is not a function.
values	values(object)	Uses Object.keys()
entries	entries(object)	Uses Object.entries()
keys	keys(object)	Uses Object.keys()
get	get(key)(object)
set	set(key, value)(object)
update	update(key, updateFn)(object)	The update function will get the current value of the specified key as it’s argument.
delete	delete(key)(object)

Usage Examples

Let’s say you have an object { q1: Number, q2: Number, q3: Number, q4: Number } which represents the number of sales per quarter. You want to:

1. Flatten this structure
2. Multiply the number of sales by their price of $99.99
3. Sum the total profits

Let’s see how some of the functions exported by this module can help you build a reusable transducer for this data.

  import { chain, map, reduce , values } from 'spicy-transducers'; 
  const sales = { q1: 33, q2: 12, q3: 40, q4: 65 }; // our input data
  const toPrice = _ => _ * 99.99; // our multiplier
  const add = (acc, _) => acc + _; // our sum function
  
  const profitsTransducer = chain(
    values,
    map(toPrice),
    reduce(add, 0)
  );
  const result = profitsTransducers(sales); // => 14998.5

Contributors

• Jovan Erčić
• Filip Danić

License

Licensed under the MIT License.

Copyright © 2017-2018 SpiceFactory