How can I transform this imperative reducer into a more declarative format using Ramda?

Question

How can I transform this imperative reducer into a more declarative format using Ramda?

I am currently working with a reducer function that aggregates values in a specific way.

The first argument is the aggregated value, while the second argument represents the next value. This function reduces over the same reaction argument, aggregating the state$ value. Each time it runs, a new aggregated value is produced.

/**
 * Applies all the reducers to create a state object.
 */
function reactionReducer(reaction: ReactionObject): ReactionObject {
    let state$ = reactionDescriptionReducer({}, reaction);
    state$ = reactionDisabledReducer(state$, reaction);
    state$ = reactionIconReducer(state$, reaction);
    state$ = reactionOrderReducer(state$, reaction);
    state$ = reactionStyleReducer(state$, reaction);
    state$ = reactionTitleReducer(state$, reaction);
    state$ = reactionTooltipReducer(state$, reaction);
    state$ = reactionVisibleReducer(state$, reaction);
    return state$;
}

const state = reactionReducer(value);

Although this setup works, I'm looking for a more flexible solution. I believe RamdaJS could provide a way to achieve this.

const state = R.????({}, value, [reactionDescriptionReducer
    reactionDisabledReducer,
    reactionIconReducer,
    reactionOrderReducer,
    reactionStyleReducer,
    reactionTitleReducer,
    reactionTooltipReducer,
    reactionVisibleReducer]);

As someone new to RamdaJS, I appreciate your patience with what may be a beginner question.

How can I utilize RamdaJS to run a chain of reducers effectively?

javascript typescript functional-programming ramda.js

Answer 1

Answer №1

and creates a fresh reducer, (r, x) => ..., by merging the two input reducers, f and g-

const and = (f, g) =>
  (r, x) => g (f (r, x), x)

all, utilizing and, forms a new reducer by combining multiple reducers-

const identity = x =>
  x

const all = (f = identity, ...more) =>
  more .reduce (and, f)

Create myReducer using all-

const myReducer =
  all
    ( disabledItemReducer
    , iconItemReducer
    , orderItemReducer
    // ...
    )

Assuming mocked implementations for these three (3) reducers are available-

const disabledItemReducer = (s, x) =>
  x < 0
    ? { ...s, disabled: true }
    : s

const iconItemReducer = (s, x) =>
  ({ ...s, icon: `${x}.png` })

const orderItemReducer = (s, x) =>
  x > 10
    ? { ...s, error: "over 10" }
    : s

Execute myReducer to observe the results-

const initState =
  { foo: "bar" }

myReducer (initState, 10)
// { foo: 'bar', icon: '10.png' }

myReducer (initState, -1)
// { foo: 'bar', disabled: true, icon: '-1.png' }

myReducer (initState, 100)
// { foo: 'bar', icon: '100.png', error: 'over 10' }

Expand the code snippet below to verify outcomes in your browser-

const identity = x =>
  x

const and = (f, g) =>
  (r, x) => g (f (r, x), x)

const all = (f, ...more) =>
  more .reduce (and, f)

const disabledItemReducer = (s, x) =>
  x < 0
    ? { ...s, disabled: true }
    : s

const iconItemReducer = (s, x) =>
  ({ ...s, icon: `${x}.png` })

const orderItemReducer = (s, x) =>
  x > 10
    ? { ...s, error: "over 10" }
    : s

const myReducer =
  all
    ( disabledItemReducer
    , iconItemReducer
    , orderItemReducer
    // ...
    )

const initState =
  { foo: "bar" }

console .log (myReducer (initState, 10))
// { foo: 'bar', icon: '10.png' }

console .log (myReducer (initState, -1))
// { foo: 'bar', disabled: true, icon: '-1.png' }

console .log (myReducer (initState, 100))
// { foo: 'bar', icon: '100.png', error: 'over 10' }

You can select any names for and and all as you prefer. They could be part of a reducer module, such as reducer.and and reducer.all

Answer 2

and creates a fresh reducer, (r, x) => ..., by merging the two input reducers, f and g-

const and = (f, g) =>
  (r, x) => g (f (r, x), x)

all, utilizing and, forms a new reducer by combining multiple reducers-

const identity = x =>
  x

const all = (f = identity, ...more) =>
  more .reduce (and, f)

Create myReducer using all-

const myReducer =
  all
    ( disabledItemReducer
    , iconItemReducer
    , orderItemReducer
    // ...
    )

Assuming mocked implementations for these three (3) reducers are available-

const disabledItemReducer = (s, x) =>
  x < 0
    ? { ...s, disabled: true }
    : s

const iconItemReducer = (s, x) =>
  ({ ...s, icon: `${x}.png` })

const orderItemReducer = (s, x) =>
  x > 10
    ? { ...s, error: "over 10" }
    : s

Execute myReducer to observe the results-

const initState =
  { foo: "bar" }

myReducer (initState, 10)
// { foo: 'bar', icon: '10.png' }

myReducer (initState, -1)
// { foo: 'bar', disabled: true, icon: '-1.png' }

myReducer (initState, 100)
// { foo: 'bar', icon: '100.png', error: 'over 10' }

Expand the code snippet below to verify outcomes in your browser-

const identity = x =>
  x

const and = (f, g) =>
  (r, x) => g (f (r, x), x)

const all = (f, ...more) =>
  more .reduce (and, f)

const disabledItemReducer = (s, x) =>
  x < 0
    ? { ...s, disabled: true }
    : s

const iconItemReducer = (s, x) =>
  ({ ...s, icon: `${x}.png` })

const orderItemReducer = (s, x) =>
  x > 10
    ? { ...s, error: "over 10" }
    : s

const myReducer =
  all
    ( disabledItemReducer
    , iconItemReducer
    , orderItemReducer
    // ...
    )

const initState =
  { foo: "bar" }

console .log (myReducer (initState, 10))
// { foo: 'bar', icon: '10.png' }

console .log (myReducer (initState, -1))
// { foo: 'bar', disabled: true, icon: '-1.png' }

console .log (myReducer (initState, 100))
// { foo: 'bar', icon: '100.png', error: 'over 10' }

You can select any names for and and all as you prefer. They could be part of a reducer module, such as reducer.and and reducer.all

Answer 3

Answer №2

One way to leverage Ramda in this scenario is by taking advantage of its support for passing functions as a monad instance to R.chain (also known as the Reader monad).

This allows you to chain together multiple functions that operate on a shared environment - in this case, the variable reaction.

We can use R.pipeWith(R.chain) to enable composing a sequence of these functions, each taking an input (such as your $state flowing through each function) and returning a new function that takes the environment as argument, generating a result to be passed to the subsequent function in the pipeline.

// Functions for illustration purposes

const reactionDescriptionReducer = ({...state}, reaction) =>
  ({ description: reaction, ...state })

const reactionDisabledReducer = ({...state}, reaction) =>
  ({ disabled: reaction, ...state })

const reactionIconReducer = ({...state}, reaction) =>
  ({ icon: reaction, ...state })

// Using `R.pipeK`
const kleisli = R.pipeWith(R.chain)

// Functions going into chain need to be curried
const curried = f => a => b => f(a, b)

// Composing the series of functions
const reactReducer = kleisli([
  curried(reactionDescriptionReducer),
  curried(reactionDisabledReducer),
  curried(reactionIconReducer)
])({})

// If all goes well...
console.log(
  reactReducer("someCommonReactionValue")
)

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.min.js"></script>

Answer 4

One way to leverage Ramda in this scenario is by taking advantage of its support for passing functions as a monad instance to R.chain (also known as the Reader monad).

This allows you to chain together multiple functions that operate on a shared environment - in this case, the variable reaction.

We can use R.pipeWith(R.chain) to enable composing a sequence of these functions, each taking an input (such as your $state flowing through each function) and returning a new function that takes the environment as argument, generating a result to be passed to the subsequent function in the pipeline.

// Functions for illustration purposes

const reactionDescriptionReducer = ({...state}, reaction) =>
  ({ description: reaction, ...state })

const reactionDisabledReducer = ({...state}, reaction) =>
  ({ disabled: reaction, ...state })

const reactionIconReducer = ({...state}, reaction) =>
  ({ icon: reaction, ...state })

// Using `R.pipeK`
const kleisli = R.pipeWith(R.chain)

// Functions going into chain need to be curried
const curried = f => a => b => f(a, b)

// Composing the series of functions
const reactReducer = kleisli([
  curried(reactionDescriptionReducer),
  curried(reactionDisabledReducer),
  curried(reactionIconReducer)
])({})

// If all goes well...
console.log(
  reactReducer("someCommonReactionValue")
)

<script src="//cdnjs.cloudflare.com/ajax/libs/ramda/0.26.1/ramda.min.js"></script>

Answer 5

Answer №3

Instead of utilizing Ramda, my initial strategy would be to keep things simple with the following approach:

const createReducer = (...functions) => (input) => functions.reduce((state, func) => func(state, input), {})

const customFunc = createReducer(
  (currentState, data) => ({...currentState, foo: `<<-${data.foo}->>`}),
  (currentState, data) => ({...currentState, bar: `=*=${data.bar}=*=`}),
  (currentState, data) => ({...currentState, baz: `-=-${data.baz}-=-`})
)

console.log(
  customFunc({foo: 'a', bar: 'b', baz: 'c'})
) //~> {foo: '<<-a->>', bar: '=*=b=*=', baz: '-=-c-=-'}

Although Ramda offers reduce and flip, their use in this particular scenario may not provide significant benefits.

Answer 6

Instead of utilizing Ramda, my initial strategy would be to keep things simple with the following approach:

const createReducer = (...functions) => (input) => functions.reduce((state, func) => func(state, input), {})

const customFunc = createReducer(
  (currentState, data) => ({...currentState, foo: `<<-${data.foo}->>`}),
  (currentState, data) => ({...currentState, bar: `=*=${data.bar}=*=`}),
  (currentState, data) => ({...currentState, baz: `-=-${data.baz}-=-`})
)

console.log(
  customFunc({foo: 'a', bar: 'b', baz: 'c'})
) //~> {foo: '<<-a->>', bar: '=*=b=*=', baz: '-=-c-=-'}

Although Ramda offers reduce and flip, their use in this particular scenario may not provide significant benefits.

How can I transform this imperative reducer into a more declarative format using Ramda?

Answer №1

Answer №2

Answer №3

Similar questions

Check to see if the item is not already in the cart, and if so, add it and then increase its quantity

Instead of using a v-if condition, add a condition directly in the Vue attribute

I encountered a problem with React Native while attempting to update the state with a new value

What is the best way to sum up multiple checkbox values in JavaScript?

What is the correct way to construct an object in TypeScript while still taking types into account?

Steps for utilizing a function from the parent component to initialize TinyMCE

Select a random class from an array of classes in JavaScript

Tips for implementing an autoscroll feature in the comments section when there is an abundance of comments

AngularJS is patiently waiting for the tag to be loaded into the DOM

Leveraging regular expressions for image domains within NextJS next.config.js

Automatic suggestions for my personalized npm module (written in ES6/Babel) in Webstorm

Guide: Building Angular/Bootstrap button checkboxes within a loop

Adding Material-UI icons dynamically in a React TypeScript project requires understanding the integration of imported icons

The MUI theme seems to be missing its application

Steps to enable Nodemailer to execute a separate .js script

The Ajax request functions flawlessly on Mozilla but encounters issues on Chrome, causing confusion as it occasionally works

Disable the setTimeout() function in order to prevent the countdown from refreshing

Topaz font does not properly display backslashes and certain characters when rendered on Canvas

Encountering an error with Angular2 when referencing node modules

Unspecified outcome of Ajax array as a choice in Select