ramda-x
v1.0.11
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This is a super slim API version of original Ramda. It has only X (10) the most important methods.
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Ramda X
Ramda X is a super small API with only 10 most important methods for functional programming. Original Ramda library is too big and abstracts almost everything away from the JavaScript language. That's why Ramda X uses the most important methods and leaves everything as it is. All implemented methods are auto-curried!!!
Important: Data comes last!
Implemented API methods:
- I. curry()
- II. compose()
- III. map() -> works only on arrays
- IV. filter() -> works only on arrays
- V. prop() -> works only on objects
prop('name')({name: 'Dimitri', location: 'Berlin'})
- VI. propEq() -> works only on objects
propEq('location', 'Berlin')
- VII. reduce() -> works only on arrays
reduce(fn, null || 'acc value', {location: Berlin})
- VIII. Task() || Task.of(x) || Task.map(), Task.chain(), Task.ap() -> for lazy evaluation and isolation of side effects
- IX. Either.Right(x) || Either.Left(x) || Either.fromNullable(x) || Either.of(x) || Either.try(f) -> for branching
Methods on the waiting list:
- composeP() -> composition with Promises
- propNotEq() -> removing a an element from an array
Additional methods for debugging Ramda X
- trace() -> can be used to debug compose/pipe
trace('label')(value)
If you want the full suite, just use the original Ramda.
Algebraic Typologies
// Source: https://github.com/DrBoolean
// Functor
Box.of(20).map(x => x / 2)
//Box(10)
// Monad
Box.of(true).chain(x => Box.of(!x))
// Box(false)
// Monoid
Box.of('small').concat(Box.of('pox'))
// Box('smallpox')
// Applicative
Box.of(x => x + 1).ap(2)
// Box(3)
// Traversable
Box.of(3).traverse(Either.x, x => fromNullable(x))
// Right(Box(3))
// Natural transformation
eitherToBox(fromNullable(null))
// Box(null)
When to use what? - Code that never fails!
const { Task, Either, Box, compose, map, fold, chain, ap, fork, trace } = require('ramda-x')
const fs = require('fs')
// we are using Task in order not to grab the state directly
// by doing so we isolate the side-effects and make our app more safely
// Use Task for side-effects: console.log, process.arg, http calls, db calls, read/write -> ASYNCHRONOUS CODE
const argv = Task((reject, resolve) => resolve(process.argv))
const httpGet = Task((reject, resolve) =>
request(url, (err, res, body) =>
err ? reject(err) : resolve(body)))
const readFile = enc => file => Task((reject, resolve) =>
fs.readFile(file, enc, (err, content) =>
err ? reject(err) : resolve(content)))
const file = readFile('utf-8')
file('config.json').fork(console.error, console.log)
// Use Eiter.try for JSON.parse/JSON.stringify -> SYNCHRONOUS CODE
const parse = Either.try(JSON.parse)
const readFileSync = Either.try(fs.readFileSync)
const result = readFileSync('config.json')
result.fold(console.error, console.log)
// Use Either.fromNullable when you are trying to get properties out of an object object.property
const first = ({ name }) =>
Either.fromNullable(name)
const name = compose(
chain(first),
Either.of
)
const myName = name({ name: 'Dimitri' })
const herName = name({ name: 'Anastasia' })
myName.fold(console.error, console.log)
herName.fold(console.error, console.log)
Either.fromNullable - Code that never fails!
const { Task, Either, prop, compose, trace, map, fold, chain } = require('ramda-x')
const findColor = name =>
({ red: '#ff4444', green: '#36599', blue: '#fff68f' })[name]
const getColor = name => Either.fromNullable(findColor(name))
const sliceBy = str => str.slice(1)
const upperCaseValue = str => str.toUpperCase()
const reportError = err => 'no color'
const showResult = fold(reportError, upperCaseValue)
const sliceByTwo = map(sliceBy)
const result = compose(
showResult,
sliceByTwo,
getColor)
result('green') // 36599
result('red') // FF4444
result('blue') // FFF68F
result('yellow') // no color
result('orange') // no color
result('white') // no color
ap && chain (Reigth/Left.chain || Right/Left.ap) - Code that never fails
const { Task, Either, prop, compose, trace, map, fold, chain } = require('ramda-x')
const fs = require('fs')
// Important: If you'll try to get a non-existing property out of the object,
//the app would not return undefined it will return 3000 as default value of the error function, defined in showResult()
const getProperty = o =>
Either.of(p => p).ap(Either.fromNullable(o.port))
const readFile = Either.try(fs.readFileSync)
const parseJSON = Either.try(JSON.parse)
const isPortAvailable = chain(getProperty)
const parse = chain(parseJSON)
const showResult = fold(
err => 3000,
c => c)
const result = compose(
showResult,
isPortAvailable,
parse,
readFile
)
result('config.json') // 8888
result('confffig.json') // 3000
Currying with Types (Boxes & Either)
const { Box } = require('ramda-x')
const add = x => y => x + y
const res = Box(add).ap(Box(20)).ap(Box(20)).fold(x => x)
console.log(
res // 40
)
//---------------------------------- // ----------------------------------
const { Task, Either, prop, compose, trace, map, fold, chain, ap } = require('ramda-x')
const $ = selector =>
Either.of({ selector, height: 10 })
const getScreenSize = screen => head => foot =>
screen - (head.height + foot.height)
const result = compose(
fold(err => 'error', x => x),
ap($('hooter')),
ap($('header')),
Either.of,
getScreenSize
)
console.log(
result(800), // 780
result(1500) // 1480
)
ap - safe and concurent IO operations - Code that never fails
const { Task, Either, prop, compose, trace, map, fold, chain, ap } = require('ramda-x')
const request = require('request')
const url1 = 'https://jsonplaceholder.typicode.com/posts/4'
const url2 = 'https://jsonplaceholder.typicode.com/posts/2'
const e = e => 'error'
const identity = x => x
const getTitle = o => Either.fromNullable(o.title).fold(e, identity)
const getId = o => Either.fromNullable(o.id).fold(e, identity)
const reportHeader = p1 => p2 =>
`Report: ${p1.fold(e, body => getTitle(body))} compared to ${p2.fold(e, body => getTitle(body))}`
const reportId = p1 => p2 =>
`Report: ${p1.fold(e, body => getId(body))} compared to ${p2.fold(e, body => getId(body))}`
const parse = Either.try(JSON.parse)
const httpGet = url =>
Task((reject, resolve) =>
request(url, (err, response, body) =>
err ? reject(err) : resolve(parse(body)))
)
const res = compose(
ap(httpGet(url2)),
ap(httpGet(url1)),
Task.of
)
res(reportHeader).fork(err => 'error', data => console.log(data))
// Report: eum et est occaecati compared to qui est esse
res(reportId).fork(err => 'error', data => console.log(data))
// Report: 4 compared to 2
ap Redux - concurrent IO operations - Code that never fails
const { Task, Either, prop, compose, trace, map, fold, chain, ap } = require('ramda-x')
const request = require('request')
const update = msg => model =>
msg.type === 'UPDATE'
? { ...model, report: msg.payload }
: msg.type === 'ERROR'
? { ...model, error: msg.error }
: model
const dispatch = msg => {
let model = {}
model = update(msg)(model)
reportHeader(model)
console.log('UPDATED MODEL', model)
}
const updateModelMsg = payload => ({ type: 'UPDATE', payload })
const updateModelErrorMsg = error => ({ type: 'ERROR', error })
const url1 = 'https://jsonplaceholder.typicode.com/posts/4'
const url2 = 'https://jsonplaceholder.typicode.com/posts/2'
const e = () => dispatch(updateModelErrorMsg('value not found'))
const identity = x => x
const getTitle = o => Either.fromNullable(o.title)
const getId = o => Either.fromNullable(o.id)
const reportHeader = p1 => p2 =>
`Report: ${p1.chain(getTitle).fold(e, identity)} compared to ${p2.chain(getTitle).fold(e, identity)}`
const reportId = p1 => p2 =>
`Report: ${p1.chain(getId).fold(e, identity)} compared to ${p2.chain(getId).fold(e, identity)}`
const parse = Either.try(JSON.parse)
const httpGet = url =>
Task((reject, resolve) =>
request(url, (err, response, body) =>
err ? reject(err) : resolve(parse(body)))
)
const res = compose(
ap(httpGet(url2)),
ap(httpGet(url1)),
Task.of
)
res(reportHeader).fork(err => dispatch(updateModelErrorMsg(err)), data => dispatch(updateModelMsg(data)))
res(reportId).fork(err => 'error', data => dispatch(updateModelMsg(data)))
// UPDATED MODEL { report: 'Report: 4 compared to 2' }
// UPDATED MODEL { report: 'Report: eum et est occaecati compared to qui est esse' }
safe I/O Operations with Parsing - Code that never fails
const { Task, Either, prop, compose, trace, map, fold, chain, ap, fork } = require('ramda-x')
const fs = require('fs')
const readFile = enc => file =>
Task((reject, resolve) =>
fs.readFile(file, enc, (err, content) =>
err ? reject(err) : resolve(content)
)
)
const writeFile = file => content =>
Task((reject, resolve) =>
fs.writeFile(file, content, (err, success) =>
err ? reject(err) : resolve('success')
)
)
const writeToConfigTwo = writeFile('config2.json')
const parse = Either.try(JSON.parse)
const stringify = Either.try(JSON.stringify)
const getProperty = b =>
Task.of(c => Either.fromNullable(c.port)).ap(b)
const eitherToTask = e =>
e.fold(Task.rejected, Task.of)
const error = e => console.log('from error:', e)
const success = c => console.log('from success', c)
const transformation = compose(
fork(error)(success),
chain(writeToConfigTwo), // Task(Task(value)) -> Task(value)
chain(eitherToTask), // Task(Right(value)) -> Task(Task(value)) -> Task(value)
map(stringify), // returns: Task(Right(value))
chain(eitherToTask), // Task(Right(value)) -> Task(Task(value)) -> Task(value)
getProperty, // returns: Task(Right(value))
chain(eitherToTask), // Task(Right(value)) -> Task(Task(value)) -> Task(value)
map(parse), // returns: Task(Right(value))
readFile('utf-8') // returns: Task(value)
)
transformation('configs.json')
Traversable with Lists
const { Task } = require('ramda-x')
const fs = require('fs')
const readFile = file =>
Task((reject, resolve) =>
fs.readFile(file, 'utf-8', (err, content) =>
err ? reject(err) : resolve(content)))
const List = xs => ({
concat: x => List(xs.concat(x)),
map: fn => List(xs.map(fn)),
reduce: (f, i) => List(xs.reduce(f, i)),
fold: f => f(xs),
traverse(of, fn) {
return xs.reduce(
(f, a) => fn(a).map(b => bs => bs.concat(b)).ap(f),
of(List([]))
)
}
})
const files = List(['config.json', 'config2.json'])
files.traverse(Task.of, fn => readFile(fn)).fork(console.error, x => x.map(x => x + '!!!').fold(x => x))
``´
### Example
```js
const { map, prop, compose, trace } = require('ramda-x')
const users = [
{ name: 'Dimitri', isAdmin: true },
{ name: 'John', isAdmin: true },
{ name: 'Mike', isAdmin: false }
]
const names = map(prop('name'), users)
console.log(names) // [ 'Dimitri', 'John', 'Mike' ]
const message = {
Records: [
{ name: 'Dimitri', isAdmin: true },
{ name: 'John', isAdmin: true },
{ name: 'Mike', isAdmin: false }
]
}
const extractNamesFromMessage = compose(
map(prop('name')),
trace('AFTER PLUCK'),
prop('Records')
)
console.log(extractNamesFromMessage(message))
// AFTER PLUCK: [
// {
// "name": "Dimitri",
// "isAdmin": true
// },
// {
// "name": "John",
// "isAdmin": true
// },
// {
// "name": "Mike",
// "isAdmin": false
// }
// ]
//[ 'Dimitri', 'John', 'Mike' ]
const filterNamesFromMessage = compose(
filter(propEq('name', 'Dimitri')),
prop('Records')
)
console.log(filterNamesFromMessage(message))
// [ { name: 'Dimitri', isAdmin: true } ]
Task - Lazy Evaluation / Isolation of Side Effects
const {Task} = require('ramda-x')
// pure function
const readFile = (filename, enc) =>
Task((reject, resolve) =>
fs.readFile(filename, enc, (err, content) =>
err ? reject(err) : resolve(content))
)
// pure function
const writeFile = (filename, contents) =>
Task((reject, resolve) =>
fs.writeFile(filename, contents, (err, success) =>
err ? reject(err) : resolve(success))
)
// pure function
const app = readFile('config.json', 'utf-8')
.map(content => content.replace(/8/g, '9'))
.chain(contents => writeFile('config2.json', contents))
// impure function with side effects
app.fork(e => console.log('error', e), succes => console.log('success'))
Lifting a value into a type
const f = x => x.concat('!!!')
const res = Task.of('hello').map(f)
res.fork(e => 'error', d => console.log(d)) // hello!!!
Either.of('hello').map(f).fold(_ => _, d => console.log(d)) // hello!!!
Try/Catch Examples
const {Either} = require('ramda-x')
const fs = require('fs')
const tryCatch = f => {
try {
return Either.Right(f())
} catch (e) {
return Either.Left(e)
}
}
const getPort = () =>
tryCatch(() => fs.readFileSync('config.json'))
.chain(c => tryCatch(() => JSON.parse(c)))
.fold(e => 3000,
c => c.port)
const res = getPort()
Try with Either.try(f)
const parse = Either.try(JSON.parse)
const eitherToTask = e =>
e.fold(Task.rejected, Task.of)
const findPost = id =>
httpGet(url(id))
.map(parse)
.chain(eitherToTask)
const main = ([id]) =>
Task.of(title => [title]).ap(findPost(id))
id.chain(main).fork(console.error, x => console.log('success', x))
Either - Instead of If/Else + Composition
import {Either} = require('ramda-x')
const fromNullable = x =>
x !== null ? Either.Right(x) : Either.Left(x)
// You can also import Either.fromNullable() and use it instead of fromNullable()
const findColor = name =>
fromNullable({ red: '#ff4444', blue: '#3b5998', yellow: '#fffG8F' }[name])
const result = findColor('yellow').map(c => c.slice(1)).fold(err => 'nothing found', c => c.toUpperCase())
Either - Instead of If/Else + Composition
const { Task, Either, prop, compose, trace, map, fold, chain } = require('ramda-x')
const { fromNullable, Right, Left } = Either
const dispatch = x => console.log('action was dispatched', x)
const getItem = o => prop('item', o)
const someAction2 = dispatch => data =>
compose(
fold(e => 'comes from the err function', x => x),
map(item => item),
map(item => item + 2),
chain(item => fromNullable(prop('item3', item))),
fromNullable
)(data)
const toUpperCase = str => str.toUpperCase()
const someAction3 = dispatch => data =>
compose(
toUpperCase,
getItem
)(data)
const prepeareAction = someAction2(dispatch)
const prepareNewAction = someAction3(dispatch)
prepeareAction(null) // comes from the err function -> the application runs without exiting
prepareNewAction(null) // TypeError: Cannot read property 'item' of null
Some other examples
const fromNullable = x =>
x !== null ? Either.Right(x) : Either.Left(x)
const tryCatch = f => {
try {
return Either.Right(f())
} catch (e) {
return Either.Left(e)
}
}
// imperative code
const openSite = () => {
if (current_user) {
return renderPage(current_user)
} else {
return showLogin()
}
}
// declarative code
const openSite = () => {
fromNullable(current_user)
.fold(showLogin, renderPage)
}
// imperative code
const getPrefs = user => {
if (user.premium) {
return loadPrefs(user.preferences)
} else {
return defaultPrefs
}
}
// declarative code
const getPrefs = user =>
(user.premium ? Right(user) : Left('not premium'))
.map(u => u.preferences)
.fold(() => defaultPrefs, prefs => loadPrefs(prefs))
// imperative code
const streetName = user => {
const address = user.address
if (address) {
const street = address.street
if (street) {
return street.name
}
}
return 'no street!'
}
// declarative code
const streetName = user =>
fromNullable(user.address)
.chain(a => fromNullable(a.street))
.map(s => s.name)
.fold(e => 'no street', n => n)
// imperative code
const concatUniq = (x, ys) => {
const found = ys.filter(y => y === x)[0]
return found ? ys : ys.concat(x)
}
// declarative code
const concatUniq = (x, ys) =>
fromNullable(ys.filter(y => y === x)[0])
.fold(() => ys.concat(x), y => ys)
// imperative code
const wrapExamples = example => {
if (example.previewPath) {
try {
example.preview = fs.readFileSync(example.previewPath)
} catch (e) { }
}
return example
}
const readFile = x => tryCatch(() => fs.readFileSync(x))
// declarative code
const wrapExamples = example => {
fromNullable(example.previewPath)
.chain(readFile)
.fold(() => example, ex => Object.assign({ preview: p }, ex))
}
// imperative code
const parseDbUrl = cfg => {
try {
const c = JSON.parse(cfg)
if(c.url) {
return c.url.match(/*....*/)
}
} catch(e) {
return null
}
}
// declarative code
const parseDbUrl = cfg => {
tryCatch(() => JSON.parse(cfg))
.chain(c => fromNullable(c.url))
.fold(e => null,
u => u.match(/*...*/))
}