apemandb/lib/helpers/integers_string.js

Database for apeman project.

/**
 * @function integersString
 */
'use strict'

/** @lends integersString */
function integersString (values) {
  return values
    .map((value) => Number(value))
    .filter((value) => typeof value !== 'undefined')
    .sort((a, b) => a - b)
    .reduce((reduced, value) => {
      let group = reduced[ reduced.length - 1 ]
      let isNext = value === (group[ group.length - 1 ] + 1)
      if (isNext) {
        group.push(value)
      } else {
        reduced.push([ value ])
      }
      return reduced
    }, [ [] ])
    .filter((group) => group.length > 0)
    .map((group) => {
      let [ first, last ] = [ group[ 0 ], group[ group.length - 1 ] ]
      return first === last ? String(first) : [ first, last ].join('..')
    }).join(',')
}

module.exports = integersString