Collection library

collection.js

import * as object from './object'

export const toObject = (collection) =>
  [ ...collection ].reduce(object.increase, {})

index.ts

export const tail = <T> (array: Array<T>): T => array[array.length - 1];

export const exceptTail = <T> (array: Array<T>): Array<T> => array.slice(0, array.length - 1);

/**
 * Convert collection to PT-BR statement.
 */

type toStatementΛ = <T> (value: T) => string;

const toStatement = <T> (
  array: Array<T>,
  λ: toStatementΛ = (value) => String(value)
): string =>
  array.length === 0 ? '' :
  array.length === 1 ? λ(array[0])
                     : exceptTail(array).map(λ).join(', ') + ' e ' + λ(tail(array));

object.js

export const increase = (object, [ property, value ]) => ({
  ...object,
  [property]: value
})