Simple pagination algorithm using lodash

createPaginations.js

import first from 'lodash/first'
import last from 'lodash/last'
import inRange from 'lodash/inRange'

export function createPagination(items, current, delta) {
  const currentIndex = items.indexOf(current)
  const left = currentIndex - delta
  const right = currentIndex + delta + 1

  const applyDots = (data, item, lastItem) => {
    const diff = item - lastItem

    if (diff === 2) {
      data.push(lastItem + 1)
    } else if (diff !== 1) {
      data.push('...')
    }

    return data
  }

  const pagination = items
    .filter((item, index) => {
      return (
        item === first(items) ||
        item === last(items) ||
        inRange(index, left, right)
      )
    })
    .reduce((data, item) => {
      const lastItem = last(data)

      if (lastItem) {
        applyDots(data, item, lastItem)
      }

      data.push(item)

      return data
    }, [])

  return pagination
}