@raini/pipes
v1.3.0
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Simple and reusable pipelines for function composition.
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@raini/pipes
@raini/pipes
is a set of composable blocks called Pipelines. Pipelines are lazy and do not get invoked until they are forked with process
method.
Pipelines are Monoids and can be concatenated with other Pipelines using p.concat
which allows joining separate sets of composed functions.
Features
- Composition of functions via
pipe
- Helper pipe methods, e.g.
pipeTap
orextendPipe
- Implements Semigroup (holds associativity) with
p.concat
- Implements Monoid (holds right identity and left identity) with
p.concat
andP.empty
- PromisePipeline allows abstracting from using Promises in composed functions -
promisePipeline.process
returns the only Promise to work with - Can be used both in Node and in browsers (transpiled to ES5)
Installation
npm i -S @raini/pipes
Usage
PromisePipeline
import { PromisePipeline } from "@raini/pipes"
import * as rl from "readline"
const addSpaceIfMissing = (q: string): string => (q.endsWith(" ") ? q : q.concat(" "))
const toObject = (q: string) => ({ q })
const createReadLine = () => ({ rl: rl.createInterface(process.stdin, process.stdout) })
const askQuestionAsync = ({ rl, q }) => new Promise((res) => rl.question(q, (a: string) => res(a)))
const applyGreenColor = (x: string) => `\x1b[32m${x}\x1b[0m`
const log = console.log
const exit = () => process.exit(0)
PromisePipeline.of(addSpaceIfMissing)
.pipe(toObject)
.pipeExtend(createReadLine) // Extend argument object with return value
.pipe(askQuestionAsync)
.pipe(applyGreenColor)
.pipeTap(log) // Execute function on the argument and return the argument
.process(() => "What is the answer to life, the universe and everything?")
.then(exit)
PromisePipeline Helpers
- pipeP is equivalent to
PromisePipeline.empty().pipe
- pipeExtendP is equivalent to
PromisePipeline.empty().pipeExtend
- pipeTapP is equivalent to
PromisePipeline.empty().pipeTap
SyncPipeline
import { SyncPipeline } from "@raini/pipes"
const isOdd = (num: number) => num % 2 == 0
const negate = <T>(f: (x: T) => any) => (x: T) => !f(x)
const filterOutOddNumbers = (nums: number[]) => nums.filter(negate(isOdd))
const multiplyBy2 = (num: number) => num * 2
const multiplyItemsBy2 = (nums: number[]) => nums.map(multiplyBy2)
const log = console.log
const result = SyncPipeline.of(filterOutOddNumbers)
.pipeTap(log) // [ 1, 3, 5 ]
.pipe(multiplyItemsBy2)
.process(() => [1, 2, 3, 4, 5])
log(result) // [ 2, 6, 10 ]
// A fun thing using pipeExtend (instead of pipe) for multiplying items by 2
const result2 = SyncPipeline.of(filterOutOddNumbers)
.pipeTap(log) // [ 1, 3, 5 ]
.pipeExtend(multiplyItemsBy2)
.process(() => [1, 2, 3, 4, 5])
log(result2) // [ 1, 3, 5, 2, 6, 10 ]
SyncPipeline Helpers
- pipe is equivalent to
SyncPipeline.empty().pipe
- pipeExtend is equivalent to
SyncPipeline.empty().pipeExtend
- pipeTap is equivalent to
SyncPipeline.empty().pipeTap