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().
reduceRight	`reduce(reduceFunction, defaultValue)(array)`	Same as Array.prototype.reduceRight().
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.
head	`head(array)`	Returns the first element from the array.
tail	`tail(array)`	Returns all elements except the first one (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:

Flatten this structure
Multiply the number of sales by their price of $99.99
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

License

Licensed under the MIT License.

spfr/spicy-transducers