perezoso-js

Perezoso JS

This library expose a series of methods like any array methods but using enumerators

We have to forms of using it

One if using everything as functions or using and object Lazy

How to use it

import { Lazy } from 'perezoso-js'

var lazy = new Lazy(1,2,3,4,5)

lazy
  .map(x => x * x) // this will return an iterable with the map values
  .filter(x => x % 3 === 0) // this will return an itereable with multiples of 3
  .value() // return the evaluation of the iterable as an Array
// returns [ 9, 36 ]

// OR
var lazy2 = Lazy.from([1,2,3,4,5,6])

lazy2
  .map(x => x * x)
  .filter(x => x % 3 === 0)
  .value()

// returns [ 9, 36 ]

or could be used in a functional way (but we don't have pipeline operator yet) (https://github.com/tc39/proposal-pipeline-operator)[https://github.com/tc39/proposal-pipeline-operator]

import { value, filter, map, compose } from 'perezoso-js/functional'

compose(
  map(x => x * x),
  filter(x => x % 3 === 0),
  value
)([1, 2, 3, 4, 5, 6])

// returns [ 9, 36 ]

You could create an Infinite iterator and use Lazy to do operations over

import { generate } from 'perezoso-js'

const Numbers = generate(function () {
  let n = 0
  return {
    next: () => ({ done: false, value: n++ })
  }
})

const Fibonacci = generate(function () {
  let n1 = 0
  let n2 = 1
  let value
  return {
    next: () => {
      [value, n1, n2] = [n1, n2, n1 + n2]
      return { value }
    }
  }
})

const rangeFactory = (from, to = Infinity, step = 1) => {
  return generate(function () {
    let done = false
    let value = 0
    return {
      next () {
        value = from
        done = from >= to
        from = !done ? from + step : value
        return { done: done, value: value }
      }
    }
  })
}

rangeFactory(1, 100)
  .map(x => x * 2)
  .filter(x => x % 4 === 0)
  .take(10)
  .value()
// [ 4, 8, 12, 16, 20, 24, 28, 32, 36, 40 ]

Numbers
  .map(x => x * 2)
  .filter(x => x % 4 === 0)
  .take(10)
  .value()
// returns [ 0, 4, 8, 12, 16, 20, 24, 28, 32, 36 ]

Fibonacci
  .map(x => x * 2)
  .filter(x => x % 4 === 0)
  .take(10)
  .value()
 // returns 0, 4, 16, 68, 288, 1220, 5168, 21892, 92736, 392836 ]