List type in JS/Node (without classes)

examples.js

import { List } from './List'

let firstList = List.of([2, 3, 4])

console.log('emit:', firstList.emit()) // => [ 2, 3, 4 ]
console.log('head:', firstList.head()) // => 2
console.log('last:', firstList.last()) // => 4
console.log('tail:', firstList.tail().emit()) // => [ 3, 4 ]


let secondList = List.of([10, 20, 30])

console.log('inspect:', secondList.inspect()) // => 'List(10,20,30)'
console.log('concat:', secondList.concat(40).emit()) // => [ 10, 20, 30, 40 ]
console.log('map:', secondList.map(v => v * 3).map(v => v * 3).emit()) // => [ 90, 180, 270 ]
console.log('chain:', secondList.chain(a => a * 200)) // => [ 2000, 4000, 6000 ]

List.js

export const List = (x) => ({
  emit: () => x,
  head: () => x[0],
  tail: () => List.of(x.splice(1)),
  last: () => x[x.length - 1],
  chain: (f) => x.map(f),
  map: (f) => List.of(x.map(f)),
  inspect: () => `List(${x})`,
  concat: (a) => List.of(x.concat(a))
})

const ListOf = (x) => (Array.isArray(x) ? List(x) : List([x]))

List.of = ListOf